diff --git a/src/.clang-tidy b/src/.clang-tidy
index 1cf270833a2..544bd5ac0c1 100644
--- a/src/.clang-tidy
+++ b/src/.clang-tidy
@@ -9,6 +9,7 @@ bugprone-lambda-function-name,
 bugprone-unhandled-self-assignment,
 misc-unused-using-decls,
 misc-no-recursion,
+modernize-deprecated-headers,
 modernize-use-default-member-init,
 modernize-use-emplace,
 modernize-use-equals-default,
@@ -29,6 +30,8 @@ readability-redundant-string-init,
 HeaderFilterRegex: '.'
 WarningsAsErrors: '*'
 CheckOptions:
+ - key: modernize-deprecated-headers.CheckHeaderFile
+   value: false
  - key: performance-move-const-arg.CheckTriviallyCopyableMove
    value: false
  - key: bugprone-unhandled-self-assignment.WarnOnlyIfThisHasSuspiciousField
diff --git a/src/base58.cpp b/src/base58.cpp
index d0e1ab465e4..19a5bd3e550 100644
--- a/src/base58.cpp
+++ b/src/base58.cpp
@@ -9,8 +9,8 @@
 #include <util/strencodings.h>
 #include <util/string.h>
 
-#include <assert.h>
-#include <string.h>
+#include <cassert>
+#include <cstring>
 
 #include <limits>
 
diff --git a/src/bech32.cpp b/src/bech32.cpp
index 81695acebaa..08bdce6dd58 100644
--- a/src/bech32.cpp
+++ b/src/bech32.cpp
@@ -7,7 +7,7 @@
 #include <util/vector.h>
 
 #include <array>
-#include <assert.h>
+#include <cassert>
 #include <numeric>
 #include <optional>
 
diff --git a/src/bech32.h b/src/bech32.h
index 6d5a68ec5a1..bc50ba54213 100644
--- a/src/bech32.h
+++ b/src/bech32.h
@@ -14,7 +14,7 @@
 #ifndef BITCOIN_BECH32_H
 #define BITCOIN_BECH32_H
 
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 #include <vector>
 
diff --git a/src/bench/examples.cpp b/src/bench/examples.cpp
index 671902ef2fb..6f5d1052ba6 100644
--- a/src/bench/examples.cpp
+++ b/src/bench/examples.cpp
@@ -5,7 +5,7 @@
 #include <bench/bench.h>
 
 // Extremely fast-running benchmark:
-#include <math.h>
+#include <cmath>
 
 volatile double sum = 0.0; // volatile, global so not optimized away
 
diff --git a/src/bench/parse_hex.cpp b/src/bench/parse_hex.cpp
index db3ead043c8..c20e9546c34 100644
--- a/src/bench/parse_hex.cpp
+++ b/src/bench/parse_hex.cpp
@@ -4,7 +4,7 @@
 
 #include <bench/bench.h>
 #include <random.h>
-#include <stddef.h>
+#include <cstddef>
 #include <util/strencodings.h>
 #include <cassert>
 #include <optional>
diff --git a/src/bip324.cpp b/src/bip324.cpp
index 73f51a195ee..bb1fae5dee4 100644
--- a/src/bip324.cpp
+++ b/src/bip324.cpp
@@ -16,7 +16,7 @@
 #include <uint256.h>
 
 #include <algorithm>
-#include <assert.h>
+#include <cassert>
 #include <cstdint>
 #include <cstddef>
 #include <iterator>
diff --git a/src/chainparamsbase.cpp b/src/chainparamsbase.cpp
index 060d519d920..24860088dd6 100644
--- a/src/chainparamsbase.cpp
+++ b/src/chainparamsbase.cpp
@@ -9,7 +9,7 @@
 #include <tinyformat.h>
 #include <util/chaintype.h>
 
-#include <assert.h>
+#include <cassert>
 
 void SetupChainParamsBaseOptions(ArgsManager& argsman)
 {
diff --git a/src/cluster_linearize.h b/src/cluster_linearize.h
index 217c4700afe..2a3c649576f 100644
--- a/src/cluster_linearize.h
+++ b/src/cluster_linearize.h
@@ -8,7 +8,7 @@
 #include <algorithm>
 #include <numeric>
 #include <optional>
-#include <stdint.h>
+#include <cstdint>
 #include <vector>
 #include <utility>
 
diff --git a/src/coins.h b/src/coins.h
index 61fb4af6420..7676f7d8702 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -16,8 +16,8 @@
 #include <util/check.h>
 #include <util/hasher.h>
 
-#include <assert.h>
-#include <stdint.h>
+#include <cassert>
+#include <cstdint>
 
 #include <functional>
 #include <unordered_map>
diff --git a/src/common/args.h b/src/common/args.h
index 8d9daf5f65d..f5dce850846 100644
--- a/src/common/args.h
+++ b/src/common/args.h
@@ -16,7 +16,7 @@
 #include <map>
 #include <optional>
 #include <set>
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 #include <variant>
 #include <vector>
diff --git a/src/consensus/consensus.h b/src/consensus/consensus.h
index cffe9cdafd7..b4e1f027768 100644
--- a/src/consensus/consensus.h
+++ b/src/consensus/consensus.h
@@ -7,7 +7,7 @@
 #define BITCOIN_CONSENSUS_CONSENSUS_H
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 /** The maximum allowed size for a serialized block, in bytes (only for buffer size limits) */
 static const unsigned int MAX_BLOCK_SERIALIZED_SIZE = 4000000;
diff --git a/src/consensus/tx_verify.h b/src/consensus/tx_verify.h
index d2cf792cf3f..845dcbf1c26 100644
--- a/src/consensus/tx_verify.h
+++ b/src/consensus/tx_verify.h
@@ -7,7 +7,7 @@
 
 #include <consensus/amount.h>
 
-#include <stdint.h>
+#include <cstdint>
 #include <vector>
 
 class CBlockIndex;
diff --git a/src/crypto/aes.cpp b/src/crypto/aes.cpp
index 2afcbd16292..b9537c7a3e7 100644
--- a/src/crypto/aes.cpp
+++ b/src/crypto/aes.cpp
@@ -4,7 +4,7 @@
 
 #include <crypto/aes.h>
 
-#include <string.h>
+#include <cstring>
 
 extern "C" {
 #include <crypto/ctaes/ctaes.c>
diff --git a/src/crypto/chacha20.cpp b/src/crypto/chacha20.cpp
index acb860e9b46..91064050f48 100644
--- a/src/crypto/chacha20.cpp
+++ b/src/crypto/chacha20.cpp
@@ -12,7 +12,7 @@
 
 #include <algorithm>
 #include <bit>
-#include <string.h>
+#include <cstring>
 
 #define QUARTERROUND(a,b,c,d) \
   a += b; d = std::rotl(d ^ a, 16); \
diff --git a/src/crypto/chacha20.h b/src/crypto/chacha20.h
index 06eb10781c5..223b317f355 100644
--- a/src/crypto/chacha20.h
+++ b/src/crypto/chacha20.h
@@ -10,7 +10,7 @@
 #include <array>
 #include <cstddef>
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 #include <utility>
 
 // classes for ChaCha20 256-bit stream cipher developed by Daniel J. Bernstein
diff --git a/src/crypto/chacha20poly1305.cpp b/src/crypto/chacha20poly1305.cpp
index 4c7da07d7ec..06dbf6037b9 100644
--- a/src/crypto/chacha20poly1305.cpp
+++ b/src/crypto/chacha20poly1305.cpp
@@ -10,7 +10,7 @@
 #include <span.h>
 #include <support/cleanse.h>
 
-#include <assert.h>
+#include <cassert>
 #include <cstddef>
 
 AEADChaCha20Poly1305::AEADChaCha20Poly1305(std::span<const std::byte> key) noexcept : m_chacha20(key)
diff --git a/src/crypto/chacha20poly1305.h b/src/crypto/chacha20poly1305.h
index 75404ca5ffd..a6c3a668cfd 100644
--- a/src/crypto/chacha20poly1305.h
+++ b/src/crypto/chacha20poly1305.h
@@ -6,7 +6,7 @@
 #define BITCOIN_CRYPTO_CHACHA20POLY1305_H
 
 #include <cstddef>
-#include <stdint.h>
+#include <cstdint>
 
 #include <crypto/chacha20.h>
 #include <crypto/poly1305.h>
diff --git a/src/crypto/hkdf_sha256_32.cpp b/src/crypto/hkdf_sha256_32.cpp
index 81f3c1349a7..4d2762b9b4d 100644
--- a/src/crypto/hkdf_sha256_32.cpp
+++ b/src/crypto/hkdf_sha256_32.cpp
@@ -4,8 +4,8 @@
 
 #include <crypto/hkdf_sha256_32.h>
 
-#include <assert.h>
-#include <string.h>
+#include <cassert>
+#include <cstring>
 
 CHKDF_HMAC_SHA256_L32::CHKDF_HMAC_SHA256_L32(const unsigned char* ikm, size_t ikmlen, const std::string& salt)
 {
diff --git a/src/crypto/hkdf_sha256_32.h b/src/crypto/hkdf_sha256_32.h
index d3735203005..3e71b0a29c6 100644
--- a/src/crypto/hkdf_sha256_32.h
+++ b/src/crypto/hkdf_sha256_32.h
@@ -8,7 +8,7 @@
 #include <crypto/hmac_sha256.h>
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 /** A rfc5869 HKDF implementation with HMAC_SHA256 and fixed key output length of 32 bytes (L=32) */
 class CHKDF_HMAC_SHA256_L32
diff --git a/src/crypto/hmac_sha256.cpp b/src/crypto/hmac_sha256.cpp
index 0ba99ae274f..2ac8d0e18b3 100644
--- a/src/crypto/hmac_sha256.cpp
+++ b/src/crypto/hmac_sha256.cpp
@@ -4,7 +4,7 @@
 
 #include <crypto/hmac_sha256.h>
 
-#include <string.h>
+#include <cstring>
 
 CHMAC_SHA256::CHMAC_SHA256(const unsigned char* key, size_t keylen)
 {
diff --git a/src/crypto/hmac_sha256.h b/src/crypto/hmac_sha256.h
index abd731d1fe5..4bcd0163abd 100644
--- a/src/crypto/hmac_sha256.h
+++ b/src/crypto/hmac_sha256.h
@@ -8,7 +8,7 @@
 #include <crypto/sha256.h>
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 /** A hasher class for HMAC-SHA-256. */
 class CHMAC_SHA256
diff --git a/src/crypto/hmac_sha512.cpp b/src/crypto/hmac_sha512.cpp
index d70aee843bd..26a988b6a6a 100644
--- a/src/crypto/hmac_sha512.cpp
+++ b/src/crypto/hmac_sha512.cpp
@@ -4,7 +4,7 @@
 
 #include <crypto/hmac_sha512.h>
 
-#include <string.h>
+#include <cstring>
 
 CHMAC_SHA512::CHMAC_SHA512(const unsigned char* key, size_t keylen)
 {
diff --git a/src/crypto/hmac_sha512.h b/src/crypto/hmac_sha512.h
index 8fa55d28444..6ea815aecf0 100644
--- a/src/crypto/hmac_sha512.h
+++ b/src/crypto/hmac_sha512.h
@@ -8,7 +8,7 @@
 #include <crypto/sha512.h>
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 /** A hasher class for HMAC-SHA-512. */
 class CHMAC_SHA512
diff --git a/src/crypto/muhash.h b/src/crypto/muhash.h
index 5137c8e2400..f3409373236 100644
--- a/src/crypto/muhash.h
+++ b/src/crypto/muhash.h
@@ -8,7 +8,7 @@
 #include <serialize.h>
 #include <uint256.h>
 
-#include <stdint.h>
+#include <cstdint>
 
 class Num3072
 {
diff --git a/src/crypto/poly1305.cpp b/src/crypto/poly1305.cpp
index 7fcbab4108d..2640e320bf9 100644
--- a/src/crypto/poly1305.cpp
+++ b/src/crypto/poly1305.cpp
@@ -5,7 +5,7 @@
 #include <crypto/common.h>
 #include <crypto/poly1305.h>
 
-#include <string.h>
+#include <cstring>
 
 namespace poly1305_donna {
 
diff --git a/src/crypto/poly1305.h b/src/crypto/poly1305.h
index 94ea69be87e..1b7e355fee1 100644
--- a/src/crypto/poly1305.h
+++ b/src/crypto/poly1305.h
@@ -9,7 +9,7 @@
 
 #include <cassert>
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 #define POLY1305_BLOCK_SIZE 16
 
diff --git a/src/crypto/ripemd160.cpp b/src/crypto/ripemd160.cpp
index a2f7c6e1563..4dad37d533e 100644
--- a/src/crypto/ripemd160.cpp
+++ b/src/crypto/ripemd160.cpp
@@ -6,7 +6,7 @@
 
 #include <crypto/common.h>
 
-#include <string.h>
+#include <cstring>
 
 // Internal implementation code.
 namespace
diff --git a/src/crypto/ripemd160.h b/src/crypto/ripemd160.h
index fb631a66d2d..888ffb51895 100644
--- a/src/crypto/ripemd160.h
+++ b/src/crypto/ripemd160.h
@@ -6,7 +6,7 @@
 #define BITCOIN_CRYPTO_RIPEMD160_H
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 /** A hasher class for RIPEMD-160. */
 class CRIPEMD160
diff --git a/src/crypto/sha1.cpp b/src/crypto/sha1.cpp
index 2610108f607..69c0bba1307 100644
--- a/src/crypto/sha1.cpp
+++ b/src/crypto/sha1.cpp
@@ -6,7 +6,7 @@
 
 #include <crypto/common.h>
 
-#include <string.h>
+#include <cstring>
 
 // Internal implementation code.
 namespace
diff --git a/src/crypto/sha1.h b/src/crypto/sha1.h
index 741cdaad58b..62ffa5d7d4a 100644
--- a/src/crypto/sha1.h
+++ b/src/crypto/sha1.h
@@ -6,7 +6,7 @@
 #define BITCOIN_CRYPTO_SHA1_H
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 /** A hasher class for SHA1. */
 class CSHA1
diff --git a/src/crypto/sha256.h b/src/crypto/sha256.h
index b1348631d32..aef61328013 100644
--- a/src/crypto/sha256.h
+++ b/src/crypto/sha256.h
@@ -6,7 +6,7 @@
 #define BITCOIN_CRYPTO_SHA256_H
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 
 /** A hasher class for SHA-256. */
diff --git a/src/crypto/sha256_avx2.cpp b/src/crypto/sha256_avx2.cpp
index df8cb7a6c98..6757a22f0aa 100644
--- a/src/crypto/sha256_avx2.cpp
+++ b/src/crypto/sha256_avx2.cpp
@@ -4,7 +4,7 @@
 
 #ifdef ENABLE_AVX2
 
-#include <stdint.h>
+#include <cstdint>
 #include <immintrin.h>
 
 #include <attributes.h>
diff --git a/src/crypto/sha256_sse4.cpp b/src/crypto/sha256_sse4.cpp
index f68e226138e..aa8bf246663 100644
--- a/src/crypto/sha256_sse4.cpp
+++ b/src/crypto/sha256_sse4.cpp
@@ -6,7 +6,7 @@
 // (available at the bottom of this file).
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 #if defined(__x86_64__) || defined(__amd64__)
 
diff --git a/src/crypto/sha256_sse41.cpp b/src/crypto/sha256_sse41.cpp
index d041fdfefc2..308de456b4b 100644
--- a/src/crypto/sha256_sse41.cpp
+++ b/src/crypto/sha256_sse41.cpp
@@ -4,7 +4,7 @@
 
 #ifdef ENABLE_SSE41
 
-#include <stdint.h>
+#include <cstdint>
 #include <immintrin.h>
 
 #include <attributes.h>
diff --git a/src/crypto/sha256_x86_shani.cpp b/src/crypto/sha256_x86_shani.cpp
index 74718281939..316cfdf5182 100644
--- a/src/crypto/sha256_x86_shani.cpp
+++ b/src/crypto/sha256_x86_shani.cpp
@@ -8,7 +8,7 @@
 
 #if defined(ENABLE_SSE41) && defined(ENABLE_X86_SHANI)
 
-#include <stdint.h>
+#include <cstdint>
 #include <immintrin.h>
 
 #include <attributes.h>
diff --git a/src/crypto/sha3.h b/src/crypto/sha3.h
index 685586af63b..6d114379f36 100644
--- a/src/crypto/sha3.h
+++ b/src/crypto/sha3.h
@@ -8,7 +8,7 @@
 #include <span.h>
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 //! The Keccak-f[1600] transform.
 void KeccakF(uint64_t (&st)[25]);
diff --git a/src/crypto/sha512.cpp b/src/crypto/sha512.cpp
index 2713f06210e..d1a5eec257e 100644
--- a/src/crypto/sha512.cpp
+++ b/src/crypto/sha512.cpp
@@ -6,7 +6,7 @@
 
 #include <crypto/common.h>
 
-#include <string.h>
+#include <cstring>
 
 // Internal implementation code.
 namespace
diff --git a/src/crypto/sha512.h b/src/crypto/sha512.h
index d2f7d6a05e4..33240229090 100644
--- a/src/crypto/sha512.h
+++ b/src/crypto/sha512.h
@@ -6,7 +6,7 @@
 #define BITCOIN_CRYPTO_SHA512_H
 
 #include <cstdlib>
-#include <stdint.h>
+#include <cstdint>
 
 /** A hasher class for SHA-512. */
 class CSHA512
diff --git a/src/crypto/siphash.h b/src/crypto/siphash.h
index c388c94951b..4c6a39e0b68 100644
--- a/src/crypto/siphash.h
+++ b/src/crypto/siphash.h
@@ -5,7 +5,7 @@
 #ifndef BITCOIN_CRYPTO_SIPHASH_H
 #define BITCOIN_CRYPTO_SIPHASH_H
 
-#include <stdint.h>
+#include <cstdint>
 
 #include <span.h>
 #include <uint256.h>
diff --git a/src/init.cpp b/src/init.cpp
index bfb42aaa3b6..588f68bf482 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -105,7 +105,7 @@
 #include <vector>
 
 #ifndef WIN32
-#include <signal.h>
+#include <csignal>
 #include <sys/stat.h>
 #endif
 
diff --git a/src/interfaces/node.h b/src/interfaces/node.h
index a17aa4afefc..2ab9f84e734 100644
--- a/src/interfaces/node.h
+++ b/src/interfaces/node.h
@@ -17,8 +17,8 @@
 
 #include <functional>
 #include <memory>
-#include <stddef.h>
-#include <stdint.h>
+#include <cstddef>
+#include <cstdint>
 #include <string>
 #include <tuple>
 #include <vector>
diff --git a/src/kernel/disconnected_transactions.cpp b/src/kernel/disconnected_transactions.cpp
index f865fed688c..f9431cef640 100644
--- a/src/kernel/disconnected_transactions.cpp
+++ b/src/kernel/disconnected_transactions.cpp
@@ -4,7 +4,7 @@
 
 #include <kernel/disconnected_transactions.h>
 
-#include <assert.h>
+#include <cassert>
 #include <core_memusage.h>
 #include <memusage.h>
 #include <primitives/transaction.h>
diff --git a/src/kernel/mempool_entry.h b/src/kernel/mempool_entry.h
index 2adeaea652d..0c3f08ba9ea 100644
--- a/src/kernel/mempool_entry.h
+++ b/src/kernel/mempool_entry.h
@@ -18,8 +18,8 @@
 #include <functional>
 #include <memory>
 #include <set>
-#include <stddef.h>
-#include <stdint.h>
+#include <cstddef>
+#include <cstdint>
 
 class CBlockIndex;
 
diff --git a/src/key_io.cpp b/src/key_io.cpp
index 6cece47e410..3e8633af36c 100644
--- a/src/key_io.cpp
+++ b/src/key_io.cpp
@@ -12,8 +12,8 @@
 #include <util/strencodings.h>
 
 #include <algorithm>
-#include <assert.h>
-#include <string.h>
+#include <cassert>
+#include <cstring>
 
 /// Maximum witness length for Bech32 addresses.
 static constexpr std::size_t BECH32_WITNESS_PROG_MAX_LEN = 40;
diff --git a/src/netbase.h b/src/netbase.h
index 3ac23050115..0ecd209a6f0 100644
--- a/src/netbase.h
+++ b/src/netbase.h
@@ -13,7 +13,7 @@
 
 #include <functional>
 #include <memory>
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 #include <type_traits>
 #include <unordered_set>
diff --git a/src/node/connection_types.h b/src/node/connection_types.h
index a911b95f7e9..037e15d866f 100644
--- a/src/node/connection_types.h
+++ b/src/node/connection_types.h
@@ -6,7 +6,7 @@
 #define BITCOIN_NODE_CONNECTION_TYPES_H
 
 #include <string>
-#include <stdint.h>
+#include <cstdint>
 
 /** Different types of connections to a peer. This enum encapsulates the
  * information we have available at the time of opening or accepting the
diff --git a/src/node/miner.h b/src/node/miner.h
index 5073d69bb1b..24651edc524 100644
--- a/src/node/miner.h
+++ b/src/node/miner.h
@@ -15,7 +15,7 @@
 
 #include <memory>
 #include <optional>
-#include <stdint.h>
+#include <cstdint>
 
 #include <boost/multi_index/identity.hpp>
 #include <boost/multi_index/indexed_by.hpp>
diff --git a/src/node/mini_miner.h b/src/node/mini_miner.h
index aec2aaf6b6b..60eb5c81ff5 100644
--- a/src/node/mini_miner.h
+++ b/src/node/mini_miner.h
@@ -13,7 +13,7 @@
 #include <memory>
 #include <optional>
 #include <set>
-#include <stdint.h>
+#include <cstdint>
 #include <vector>
 
 class CFeeRate;
diff --git a/src/pow.h b/src/pow.h
index ceba55d36a2..dbf9a673293 100644
--- a/src/pow.h
+++ b/src/pow.h
@@ -8,7 +8,7 @@
 
 #include <consensus/params.h>
 
-#include <stdint.h>
+#include <cstdint>
 
 class CBlockHeader;
 class CBlockIndex;
diff --git a/src/qt/bitcoin.h b/src/qt/bitcoin.h
index 52b117eed7c..142a7e2da56 100644
--- a/src/qt/bitcoin.h
+++ b/src/qt/bitcoin.h
@@ -10,7 +10,7 @@
 #include <interfaces/node.h>
 #include <qt/initexecutor.h>
 
-#include <assert.h>
+#include <cassert>
 #include <memory>
 #include <optional>
 
diff --git a/src/qt/clientmodel.cpp b/src/qt/clientmodel.cpp
index fb81dee8daa..b923ffe8dad 100644
--- a/src/qt/clientmodel.cpp
+++ b/src/qt/clientmodel.cpp
@@ -23,7 +23,7 @@
 #include <util/time.h>
 #include <validation.h>
 
-#include <stdint.h>
+#include <cstdint>
 
 #include <QDebug>
 #include <QMetaObject>
diff --git a/src/qt/notificator.cpp b/src/qt/notificator.cpp
index af97bb21437..47a21cf898e 100644
--- a/src/qt/notificator.cpp
+++ b/src/qt/notificator.cpp
@@ -18,7 +18,7 @@
 #ifdef USE_DBUS
 #include <QDBusMetaType>
 #include <QtDBus>
-#include <stdint.h>
+#include <cstdint>
 #endif
 #ifdef Q_OS_MACOS
 #include <qt/macnotificationhandler.h>
diff --git a/src/qt/optionsmodel.h b/src/qt/optionsmodel.h
index c24b35ed793..efe9b3bd4df 100644
--- a/src/qt/optionsmodel.h
+++ b/src/qt/optionsmodel.h
@@ -12,7 +12,7 @@
 #include <QAbstractListModel>
 #include <QFont>
 
-#include <assert.h>
+#include <cassert>
 #include <variant>
 
 struct bilingual_str;
diff --git a/src/qt/transactiondesc.cpp b/src/qt/transactiondesc.cpp
index 4d902f2cd28..74ddb35c191 100644
--- a/src/qt/transactiondesc.cpp
+++ b/src/qt/transactiondesc.cpp
@@ -19,7 +19,7 @@
 #include <validation.h>
 #include <wallet/types.h>
 
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 
 #include <QLatin1String>
diff --git a/src/qt/transactionrecord.cpp b/src/qt/transactionrecord.cpp
index 5f9e37aac8e..cce453acf3e 100644
--- a/src/qt/transactionrecord.cpp
+++ b/src/qt/transactionrecord.cpp
@@ -9,7 +9,7 @@
 #include <key_io.h>
 #include <wallet/types.h>
 
-#include <stdint.h>
+#include <cstdint>
 
 #include <QDateTime>
 
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index a237a24c84e..d5ce1bd4696 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -52,7 +52,7 @@
 #include <validationinterface.h>
 #include <versionbits.h>
 
-#include <stdint.h>
+#include <cstdint>
 
 #include <condition_variable>
 #include <iterator>
diff --git a/src/rpc/blockchain.h b/src/rpc/blockchain.h
index 954ede6519b..649c1dddec8 100644
--- a/src/rpc/blockchain.h
+++ b/src/rpc/blockchain.h
@@ -13,7 +13,7 @@
 #include <validation.h>
 
 #include <any>
-#include <stdint.h>
+#include <cstdint>
 #include <vector>
 
 class CBlock;
diff --git a/src/rpc/client.cpp b/src/rpc/client.cpp
index 08bd1142fce..74e091224bd 100644
--- a/src/rpc/client.cpp
+++ b/src/rpc/client.cpp
@@ -8,7 +8,7 @@
 #include <tinyformat.h>
 
 #include <set>
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 #include <string_view>
 
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index aa68ae324dd..ef234c6283e 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -44,7 +44,7 @@
 #include <validationinterface.h>
 
 #include <memory>
-#include <stdint.h>
+#include <cstdint>
 
 using interfaces::BlockRef;
 using interfaces::BlockTemplate;
diff --git a/src/rpc/node.cpp b/src/rpc/node.cpp
index 232a1d16f4e..60f7c398582 100644
--- a/src/rpc/node.cpp
+++ b/src/rpc/node.cpp
@@ -26,7 +26,7 @@
 #include <util/check.h>
 #include <util/time.h>
 
-#include <stdint.h>
+#include <cstdint>
 #ifdef HAVE_MALLOC_INFO
 #include <malloc.h>
 #endif
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 8f7b9769a8e..93541a93300 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -43,7 +43,7 @@
 #include <validationinterface.h>
 
 #include <numeric>
-#include <stdint.h>
+#include <cstdint>
 
 #include <univalue.h>
 
diff --git a/src/rpc/server.h b/src/rpc/server.h
index 5a22279a58e..a14897f390c 100644
--- a/src/rpc/server.h
+++ b/src/rpc/server.h
@@ -11,7 +11,7 @@
 
 #include <functional>
 #include <map>
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 
 #include <univalue.h>
diff --git a/src/streams.h b/src/streams.h
index 1ebcff3671f..0b3b939fabd 100644
--- a/src/streams.h
+++ b/src/streams.h
@@ -12,14 +12,14 @@
 #include <util/overflow.h>
 
 #include <algorithm>
-#include <assert.h>
+#include <cassert>
 #include <cstddef>
 #include <cstdio>
 #include <ios>
 #include <limits>
 #include <optional>
-#include <stdint.h>
-#include <string.h>
+#include <cstdint>
+#include <cstring>
 #include <string>
 #include <utility>
 #include <vector>
diff --git a/src/test/compress_tests.cpp b/src/test/compress_tests.cpp
index 7e17e6ef939..c8289a281f9 100644
--- a/src/test/compress_tests.cpp
+++ b/src/test/compress_tests.cpp
@@ -7,7 +7,7 @@
 #include <test/util/random.h>
 #include <test/util/setup_common.h>
 
-#include <stdint.h>
+#include <cstdint>
 
 #include <boost/test/unit_test.hpp>
 
diff --git a/src/test/denialofservice_tests.cpp b/src/test/denialofservice_tests.cpp
index 9ee7e9c9fe2..800a9eac247 100644
--- a/src/test/denialofservice_tests.cpp
+++ b/src/test/denialofservice_tests.cpp
@@ -21,7 +21,7 @@
 #include <validation.h>
 
 #include <array>
-#include <stdint.h>
+#include <cstdint>
 
 #include <boost/test/unit_test.hpp>
 
diff --git a/src/test/fuzz/addrman.cpp b/src/test/fuzz/addrman.cpp
index dedea850803..bce7e64ac7b 100644
--- a/src/test/fuzz/addrman.cpp
+++ b/src/test/fuzz/addrman.cpp
@@ -14,7 +14,7 @@
 #include <test/fuzz/util.h>
 #include <test/fuzz/util/net.h>
 #include <test/util/setup_common.h>
-#include <time.h>
+#include <ctime>
 #include <util/asmap.h>
 #include <util/chaintype.h>
 
diff --git a/src/test/fuzz/asmap_direct.cpp b/src/test/fuzz/asmap_direct.cpp
index 8a355fd3f60..16c70a582b3 100644
--- a/src/test/fuzz/asmap_direct.cpp
+++ b/src/test/fuzz/asmap_direct.cpp
@@ -10,7 +10,7 @@
 #include <optional>
 #include <vector>
 
-#include <assert.h>
+#include <cassert>
 
 FUZZ_TARGET(asmap_direct)
 {
diff --git a/src/test/fuzz/cluster_linearize.cpp b/src/test/fuzz/cluster_linearize.cpp
index fb4bf3a719f..5ac9edfc69e 100644
--- a/src/test/fuzz/cluster_linearize.cpp
+++ b/src/test/fuzz/cluster_linearize.cpp
@@ -13,7 +13,7 @@
 #include <util/feefrac.h>
 
 #include <algorithm>
-#include <stdint.h>
+#include <cstdint>
 #include <vector>
 #include <utility>
 
diff --git a/src/test/fuzz/coinscache_sim.cpp b/src/test/fuzz/coinscache_sim.cpp
index 6000d52fc97..dac6f4ab4b6 100644
--- a/src/test/fuzz/coinscache_sim.cpp
+++ b/src/test/fuzz/coinscache_sim.cpp
@@ -9,10 +9,10 @@
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/util.h>
 
-#include <assert.h>
+#include <cassert>
 #include <optional>
 #include <memory>
-#include <stdint.h>
+#include <cstdint>
 #include <vector>
 
 namespace {
diff --git a/src/test/fuzz/deserialize.cpp b/src/test/fuzz/deserialize.cpp
index 270d546c394..46ac0785136 100644
--- a/src/test/fuzz/deserialize.cpp
+++ b/src/test/fuzz/deserialize.cpp
@@ -32,7 +32,7 @@
 #include <exception>
 #include <optional>
 #include <stdexcept>
-#include <stdint.h>
+#include <cstdint>
 
 using node::SnapshotMetadata;
 
diff --git a/src/test/fuzz/feeratediagram.cpp b/src/test/fuzz/feeratediagram.cpp
index 1a700987d67..6dcc63e91e2 100644
--- a/src/test/fuzz/feeratediagram.cpp
+++ b/src/test/fuzz/feeratediagram.cpp
@@ -2,7 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <stdint.h>
+#include <cstdint>
 
 #include <vector>
 
@@ -12,7 +12,7 @@
 #include <test/fuzz/fuzz.h>
 #include <test/fuzz/util.h>
 
-#include <assert.h>
+#include <cassert>
 
 namespace {
 
diff --git a/src/test/fuzz/txgraph.cpp b/src/test/fuzz/txgraph.cpp
index 2c9fda9cd93..7f7a3181b16 100644
--- a/src/test/fuzz/txgraph.cpp
+++ b/src/test/fuzz/txgraph.cpp
@@ -15,7 +15,7 @@
 #include <map>
 #include <memory>
 #include <set>
-#include <stdint.h>
+#include <cstdint>
 #include <utility>
 
 using namespace cluster_linearize;
diff --git a/src/test/fuzz/vecdeque.cpp b/src/test/fuzz/vecdeque.cpp
index 9a71c43b987..13843b2c4b0 100644
--- a/src/test/fuzz/vecdeque.cpp
+++ b/src/test/fuzz/vecdeque.cpp
@@ -8,7 +8,7 @@
 #include <util/vecdeque.h>
 
 #include <deque>
-#include <stdint.h>
+#include <cstdint>
 
 namespace {
 
diff --git a/src/test/scriptnum10.h b/src/test/scriptnum10.h
index 1381d5d431d..42ab8e94053 100644
--- a/src/test/scriptnum10.h
+++ b/src/test/scriptnum10.h
@@ -6,10 +6,10 @@
 #ifndef BITCOIN_TEST_SCRIPTNUM10_H
 #define BITCOIN_TEST_SCRIPTNUM10_H
 
-#include <assert.h>
+#include <cassert>
 #include <limits>
 #include <stdexcept>
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 #include <vector>
 
diff --git a/src/test/scriptnum_tests.cpp b/src/test/scriptnum_tests.cpp
index 746d4d3c6b8..caaacc71354 100644
--- a/src/test/scriptnum_tests.cpp
+++ b/src/test/scriptnum_tests.cpp
@@ -7,8 +7,8 @@
 #include <test/util/setup_common.h>
 
 #include <boost/test/unit_test.hpp>
-#include <limits.h>
-#include <stdint.h>
+#include <climits>
+#include <cstdint>
 
 BOOST_FIXTURE_TEST_SUITE(scriptnum_tests, BasicTestingSetup)
 
diff --git a/src/test/serialize_tests.cpp b/src/test/serialize_tests.cpp
index 9c68c8bb964..33a9133d2e2 100644
--- a/src/test/serialize_tests.cpp
+++ b/src/test/serialize_tests.cpp
@@ -8,7 +8,7 @@
 #include <test/util/setup_common.h>
 #include <util/strencodings.h>
 
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 
 #include <boost/test/unit_test.hpp>
diff --git a/src/test/util/cluster_linearize.h b/src/test/util/cluster_linearize.h
index fa7945aac65..b69edb496b3 100644
--- a/src/test/util/cluster_linearize.h
+++ b/src/test/util/cluster_linearize.h
@@ -12,7 +12,7 @@
 #include <util/bitset.h>
 #include <util/feefrac.h>
 
-#include <stdint.h>
+#include <cstdint>
 #include <numeric>
 #include <vector>
 #include <utility>
diff --git a/src/test/util/coins.cpp b/src/test/util/coins.cpp
index 7e10c7c58d3..aea01d12fd8 100644
--- a/src/test/util/coins.cpp
+++ b/src/test/util/coins.cpp
@@ -10,7 +10,7 @@
 #include <test/util/random.h>
 #include <uint256.h>
 
-#include <stdint.h>
+#include <cstdint>
 #include <utility>
 
 COutPoint AddTestCoin(FastRandomContext& rng, CCoinsViewCache& coins_view)
diff --git a/src/txgraph.h b/src/txgraph.h
index 9cfbe70acdc..6fa035fb5b8 100644
--- a/src/txgraph.h
+++ b/src/txgraph.h
@@ -5,7 +5,7 @@
 #include <compare>
 #include <memory>
 #include <optional>
-#include <stdint.h>
+#include <cstdint>
 #include <vector>
 #include <utility>
 
diff --git a/src/txrequest.cpp b/src/txrequest.cpp
index 5909146427b..1e40bb75bc0 100644
--- a/src/txrequest.cpp
+++ b/src/txrequest.cpp
@@ -21,7 +21,7 @@
 #include <unordered_map>
 #include <utility>
 
-#include <assert.h>
+#include <cassert>
 
 namespace {
 
diff --git a/src/util/feefrac.h b/src/util/feefrac.h
index c29dabc43b4..7b3e6010d64 100644
--- a/src/util/feefrac.h
+++ b/src/util/feefrac.h
@@ -5,7 +5,7 @@
 #ifndef BITCOIN_UTIL_FEEFRAC_H
 #define BITCOIN_UTIL_FEEFRAC_H
 
-#include <stdint.h>
+#include <cstdint>
 #include <compare>
 #include <vector>
 #include <span.h>
diff --git a/src/util/tokenpipe.cpp b/src/util/tokenpipe.cpp
index 9425c62ebfc..1948beb7c2d 100644
--- a/src/util/tokenpipe.cpp
+++ b/src/util/tokenpipe.cpp
@@ -7,7 +7,7 @@
 
 #ifndef WIN32
 
-#include <errno.h>
+#include <cerrno>
 #include <fcntl.h>
 #include <optional>
 #include <unistd.h>
diff --git a/src/validation.h b/src/validation.h
index 0a8a94db120..05a2a2df8c0 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -41,7 +41,7 @@
 #include <optional>
 #include <set>
 #include <span>
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 #include <type_traits>
 #include <utility>
diff --git a/src/wallet/sqlite.cpp b/src/wallet/sqlite.cpp
index 9b6215f9371..c53b6935b1b 100644
--- a/src/wallet/sqlite.cpp
+++ b/src/wallet/sqlite.cpp
@@ -17,7 +17,7 @@
 #include <wallet/db.h>
 
 #include <sqlite3.h>
-#include <stdint.h>
+#include <cstdint>
 
 #include <optional>
 #include <utility>
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index 966c6d2c4ba..eda4b4d4992 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -6,7 +6,7 @@
 
 #include <future>
 #include <memory>
-#include <stdint.h>
+#include <cstdint>
 #include <vector>
 
 #include <addresstype.h>
diff --git a/src/wallet/walletdb.h b/src/wallet/walletdb.h
index 507b79e7a35..e576739bbe4 100644
--- a/src/wallet/walletdb.h
+++ b/src/wallet/walletdb.h
@@ -12,7 +12,7 @@
 #include <wallet/walletutil.h>
 #include <key.h>
 
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 #include <vector>