diff --git a/stl/inc/charconv b/stl/inc/charconv
index 75021352e64..85a83419bee 100644
--- a/stl/inc/charconv
+++ b/stl/inc/charconv
@@ -35,7 +35,7 @@ inline constexpr char _Charconv_digits[] = {'0', '1', '2', '3', '4', '5', '6', '
 _STL_INTERNAL_STATIC_ASSERT(_STD size(_Charconv_digits) == 36);
 
 template <class _RawTy>
-_NODISCARD to_chars_result _Integer_to_chars(
+_NODISCARD _CONSTEXPR23 to_chars_result _Integer_to_chars(
     char* _First, char* const _Last, const _RawTy _Raw_value, const int _Base) noexcept {
     _Adl_verify_range(_First, _Last);
     _STL_ASSERT(_Base >= 2 && _Base <= 36, "invalid base in to_chars()");
@@ -152,52 +152,52 @@ _NODISCARD to_chars_result _Integer_to_chars(
         return {_Last, errc::value_too_large};
     }
 
-    _CSTD memcpy(_First, _RNext, static_cast<size_t>(_Digits_written));
+    _Copy_n_unchecked4(_RNext, _Digits_written, _First);
 
     return {_First + _Digits_written, errc{}};
 }
 
-inline to_chars_result to_chars(char* const _First, char* const _Last, const char _Value, const int _Base = 10) noexcept
-/* strengthened */ {
+_CONSTEXPR23 to_chars_result to_chars(
+    char* const _First, char* const _Last, const char _Value, const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(
+_CONSTEXPR23 to_chars_result to_chars(
     char* const _First, char* const _Last, const signed char _Value, const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned char _Value,
+_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned char _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(
+_CONSTEXPR23 to_chars_result to_chars(
     char* const _First, char* const _Last, const short _Value, const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned short _Value,
+_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned short _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(char* const _First, char* const _Last, const int _Value, const int _Base = 10) noexcept
-/* strengthened */ {
+_CONSTEXPR23 to_chars_result to_chars(
+    char* const _First, char* const _Last, const int _Value, const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned int _Value,
+_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned int _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(char* const _First, char* const _Last, const long _Value, const int _Base = 10) noexcept
-/* strengthened */ {
+_CONSTEXPR23 to_chars_result to_chars(
+    char* const _First, char* const _Last, const long _Value, const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned long _Value,
+_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned long _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(
+_CONSTEXPR23 to_chars_result to_chars(
     char* const _First, char* const _Last, const long long _Value, const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
-inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned long long _Value,
+_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned long long _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_to_chars(_First, _Last, _Value, _Base);
 }
@@ -213,27 +213,27 @@ struct from_chars_result {
 #endif // _HAS_CXX20
 };
 
-_NODISCARD inline unsigned char _Digit_from_char(const char _Ch) noexcept {
+// convert ['0', '9'] ['A', 'Z'] ['a', 'z'] to [0, 35], everything else to 255
+inline constexpr unsigned char _Digit_from_byte[] = {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255,
+    255, 255, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
+    255, 255, 255, 255, 255, 255, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
+    31, 32, 33, 34, 35, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255};
+_STL_INTERNAL_STATIC_ASSERT(_STD size(_Digit_from_byte) == 256);
+
+_NODISCARD _CONSTEXPR23 unsigned char _Digit_from_char(const char _Ch) noexcept {
     // convert ['0', '9'] ['A', 'Z'] ['a', 'z'] to [0, 35], everything else to 255
-    static constexpr unsigned char _Digit_from_byte[] = {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255,
-        255, 255, 255, 255, 255, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
-        32, 33, 34, 35, 255, 255, 255, 255, 255, 255, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
-        26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-        255, 255, 255, 255, 255, 255, 255, 255, 255};
-    _STL_INTERNAL_STATIC_ASSERT(_STD size(_Digit_from_byte) == 256);
-
     return _Digit_from_byte[static_cast<unsigned char>(_Ch)];
 }
 
 template <class _RawTy>
-_NODISCARD from_chars_result _Integer_from_chars(
+_NODISCARD _CONSTEXPR23 from_chars_result _Integer_from_chars(
     const char* const _First, const char* const _Last, _RawTy& _Raw_value, const int _Base) noexcept {
     _Adl_verify_range(_First, _Last);
     _STL_ASSERT(_Base >= 2 && _Base <= 36, "invalid base in from_chars()");
@@ -309,47 +309,47 @@ _NODISCARD from_chars_result _Integer_from_chars(
     return {_Next, errc{}};
 }
 
-inline from_chars_result from_chars(
+_CONSTEXPR23 from_chars_result from_chars(
     const char* const _First, const char* const _Last, char& _Value, const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(const char* const _First, const char* const _Last, signed char& _Value,
+_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, signed char& _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned char& _Value,
+_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned char& _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(const char* const _First, const char* const _Last, short& _Value,
+_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, short& _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned short& _Value,
+_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned short& _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(
+_CONSTEXPR23 from_chars_result from_chars(
     const char* const _First, const char* const _Last, int& _Value, const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned int& _Value,
+_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned int& _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(
+_CONSTEXPR23 from_chars_result from_chars(
     const char* const _First, const char* const _Last, long& _Value, const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned long& _Value,
+_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned long& _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(const char* const _First, const char* const _Last, long long& _Value,
+_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, long long& _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
-inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned long long& _Value,
+_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned long long& _Value,
     const int _Base = 10) noexcept /* strengthened */ {
     return _Integer_from_chars(_First, _Last, _Value, _Base);
 }
diff --git a/stl/inc/yvals_core.h b/stl/inc/yvals_core.h
index 68ad8fa7c49..25e51c30bed 100644
--- a/stl/inc/yvals_core.h
+++ b/stl/inc/yvals_core.h
@@ -321,6 +321,7 @@
 // P2166R1 Prohibiting basic_string And basic_string_view Construction From nullptr
 // P2186R2 Removing Garbage Collection Support
 // P2273R3 constexpr unique_ptr
+// P2291R3 constexpr Integral <charconv>
 // P2302R4 ranges::contains, ranges::contains_subrange
 // P2321R2 zip
 //     (changes to pair, tuple, and vector<bool>::reference only)
@@ -1496,6 +1497,7 @@ _EMIT_STL_ERROR(STL1004, "C++98 unexpected() is incompatible with C++23 unexpect
 #define __cpp_lib_bind_back                         202202L
 #define __cpp_lib_byteswap                          202110L
 #define __cpp_lib_constexpr_bitset                  202207L
+#define __cpp_lib_constexpr_charconv                202207L
 #define __cpp_lib_constexpr_typeinfo                202106L
 
 #ifdef __cpp_lib_concepts
diff --git a/tests/std/tests/P0067R5_charconv/test.cpp b/tests/std/tests/P0067R5_charconv/test.cpp
index 5b0da2c4d24..d2d1ba0f378 100644
--- a/tests/std/tests/P0067R5_charconv/test.cpp
+++ b/tests/std/tests/P0067R5_charconv/test.cpp
@@ -197,9 +197,11 @@ void test_common_to_chars(
 }
 
 template <typename T>
-void test_integer_to_chars(const T value, const optional<int> opt_base, const string_view correct) {
-
-    test_common_to_chars(value, opt_base, nullopt, correct);
+_CONSTEXPR23 void test_integer_to_chars(const T value, const optional<int> opt_base, const string_view correct) {
+    // This reaches the constexpr step limit too quickly
+    if (!_Is_constant_evaluated()) {
+        test_common_to_chars(value, opt_base, nullopt, correct);
+    }
 
     { // Also test successful from_chars() scenarios.
         const char* const correct_first = correct.data();
@@ -387,7 +389,7 @@ constexpr pair<int64_t, array<const char*, 37>> output_negative[] = {
 };
 
 template <typename T>
-void test_integer_to_chars() {
+_CONSTEXPR23 bool test_integer_to_chars() {
     for (int base = 2; base <= 36; ++base) {
         test_integer_to_chars(static_cast<T>(0), base, "0");
         test_integer_to_chars(static_cast<T>(1), base, "1");
@@ -413,12 +415,14 @@ void test_integer_to_chars() {
     }
 
     test_integer_to_chars(static_cast<T>(42), nullopt, "42");
+
+    return true;
 }
 
 enum class TestFromCharsMode { Normal, SignalingNaN };
 
 template <typename T, typename BaseOrFmt>
-void test_from_chars(const string_view input, const BaseOrFmt base_or_fmt, const size_t correct_idx,
+_CONSTEXPR23 void test_from_chars(const string_view input, const BaseOrFmt base_or_fmt, const size_t correct_idx,
     const errc correct_ec, const optional<T> opt_correct = nullopt,
     const TestFromCharsMode mode = TestFromCharsMode::Normal) {
 
@@ -460,7 +464,17 @@ constexpr errc inv_arg = errc::invalid_argument;
 constexpr errc out_ran = errc::result_out_of_range;
 
 template <typename T>
-void test_integer_from_chars() {
+_CONSTEXPR23 bool test_integer_from_chars() {
+    const string hundred_zeroes(100, '0');
+    const string hundred_zeroes_and_11       = hundred_zeroes + "11"s;
+    const string minus_hundred_zeroes        = "-"s + hundred_zeroes;
+    const string minus_hundred_zeroes_and_11 = "-"s + hundred_zeroes_and_11;
+
+    const string hundred_ones(100, '1');
+    const string hundred_ones_and_atatat       = hundred_ones + "@@@"s;
+    const string minus_hundred_ones            = "-"s + hundred_ones;
+    const string minus_hundred_ones_and_atatat = "-"s + hundred_ones_and_atatat;
+
     for (int base = 2; base <= 36; ++base) {
         test_from_chars<T>("", base, 0, inv_arg); // no characters
         test_from_chars<T>("@1", base, 0, inv_arg); // '@' is bogus
@@ -497,14 +511,14 @@ void test_integer_from_chars() {
         }
 
         // Test leading zeroes.
-        test_from_chars<T>(string(100, '0'), base, 100, errc{}, static_cast<T>(0));
-        test_from_chars<T>(string(100, '0') + "11"s, base, 102, errc{}, static_cast<T>(base + 1));
+        test_from_chars<T>(hundred_zeroes, base, 100, errc{}, static_cast<T>(0));
+        test_from_chars<T>(hundred_zeroes_and_11, base, 102, errc{}, static_cast<T>(base + 1));
 
         // Test negative zero and negative leading zeroes.
         if constexpr (is_signed_v<T>) {
             test_from_chars<T>("-0", base, 2, errc{}, static_cast<T>(0));
-            test_from_chars<T>("-"s + string(100, '0'), base, 101, errc{}, static_cast<T>(0));
-            test_from_chars<T>("-"s + string(100, '0') + "11"s, base, 103, errc{}, static_cast<T>(-base - 1));
+            test_from_chars<T>(minus_hundred_zeroes, base, 101, errc{}, static_cast<T>(0));
+            test_from_chars<T>(minus_hundred_zeroes_and_11, base, 103, errc{}, static_cast<T>(-base - 1));
         }
 
         // N4713 23.20.3 [charconv.from.chars]/1 "The member ptr of the return value points to the
@@ -513,12 +527,12 @@ void test_integer_from_chars() {
         test_from_chars<T>("11@@@", base, 2, errc{}, static_cast<T>(base + 1));
 
         // When overflowing, we need to keep consuming valid digits, in order to return ptr correctly.
-        test_from_chars<T>(string(100, '1'), base, 100, out_ran);
-        test_from_chars<T>(string(100, '1') + "@@@"s, base, 100, out_ran);
+        test_from_chars<T>(hundred_ones, base, 100, out_ran);
+        test_from_chars<T>(hundred_ones_and_atatat, base, 100, out_ran);
 
         if constexpr (is_signed_v<T>) {
-            test_from_chars<T>("-"s + string(100, '1'), base, 101, out_ran);
-            test_from_chars<T>("-"s + string(100, '1') + "@@@"s, base, 101, out_ran);
+            test_from_chars<T>(minus_hundred_ones, base, 101, out_ran);
+            test_from_chars<T>(minus_hundred_ones_and_atatat, base, 101, out_ran);
         }
     }
 
@@ -538,27 +552,22 @@ void test_integer_from_chars() {
         test_from_chars<T>("-0x1729", 16, 2, errc{}, static_cast<T>(0)); // reads "-0", stops at 'x'
         test_from_chars<T>("-0X1729", 16, 2, errc{}, static_cast<T>(0)); // reads "-0", stops at 'X'
     }
+
+    return true;
 }
 
 template <typename T>
 void test_integer() {
     test_integer_to_chars<T>();
     test_integer_from_chars<T>();
-}
 
-void all_integer_tests() {
-    test_integer<char>();
-    test_integer<signed char>();
-    test_integer<unsigned char>();
-    test_integer<short>();
-    test_integer<unsigned short>();
-    test_integer<int>();
-    test_integer<unsigned int>();
-    test_integer<long>();
-    test_integer<unsigned long>();
-    test_integer<long long>();
-    test_integer<unsigned long long>();
+#if _HAS_CXX23
+    static_assert(test_integer_to_chars<T>());
+    static_assert(test_integer_from_chars<T>());
+#endif // _HAS_CXX23
+}
 
+_CONSTEXPR23 bool test_integer_overflow_scenarios() {
     // Test overflow scenarios.
     test_from_chars<unsigned int>("4294967289", 10, 10, errc{}, 4294967289U); // not risky
     test_from_chars<unsigned int>("4294967294", 10, 10, errc{}, 4294967294U); // risky with good digit
@@ -577,6 +586,27 @@ void all_integer_tests() {
     test_from_chars<int>("-2147483648", 10, 11, errc{}, -2147483647 - 1); // risky with max digit
     test_from_chars<int>("-2147483649", 10, 11, out_ran); // risky with bad digit
     test_from_chars<int>("-2147483650", 10, 11, out_ran); // beyond risky
+
+    return true;
+}
+
+void all_integer_tests() {
+    test_integer<char>();
+    test_integer<signed char>();
+    test_integer<unsigned char>();
+    test_integer<short>();
+    test_integer<unsigned short>();
+    test_integer<int>();
+    test_integer<unsigned int>();
+    test_integer<long>();
+    test_integer<unsigned long>();
+    test_integer<long long>();
+    test_integer<unsigned long long>();
+
+    test_integer_overflow_scenarios();
+#if _HAS_CXX23
+    static_assert(test_integer_overflow_scenarios());
+#endif // _HAS_CXX23
 }
 
 void assert_message_bits(const bool b, const char* const msg, const uint32_t bits) {
diff --git a/tests/std/tests/VSO_0157762_feature_test_macros/test.compile.pass.cpp b/tests/std/tests/VSO_0157762_feature_test_macros/test.compile.pass.cpp
index 8d20d002e40..d47fa0d042c 100644
--- a/tests/std/tests/VSO_0157762_feature_test_macros/test.compile.pass.cpp
+++ b/tests/std/tests/VSO_0157762_feature_test_macros/test.compile.pass.cpp
@@ -500,6 +500,20 @@ STATIC_ASSERT(__cpp_lib_constexpr_bitset == 202207L);
 #endif
 #endif
 
+#if _HAS_CXX23
+#ifndef __cpp_lib_constexpr_charconv
+#error __cpp_lib_constexpr_charconv is not defined
+#elif __cpp_lib_constexpr_charconv != 202207L
+#error __cpp_lib_constexpr_charconv  is not 202207L
+#else
+STATIC_ASSERT(__cpp_lib_constexpr_charconv == 202207L);
+#endif
+#else
+#ifdef __cpp_lib_constexpr_charconv
+#error __cpp_lib_constexpr_charconv is defined
+#endif
+#endif
+
 #if _HAS_CXX20
 #ifndef __cpp_lib_constexpr_complex
 #error __cpp_lib_constexpr_complex is not defined