diff --git a/include/boost/int128/detail/mini_from_chars.hpp b/include/boost/int128/detail/mini_from_chars.hpp
index f1c2af6a..0db8ac56 100644
--- a/include/boost/int128/detail/mini_from_chars.hpp
+++ b/include/boost/int128/detail/mini_from_chars.hpp
@@ -28,7 +28,7 @@ namespace impl {
 BOOST_INT128_INLINE_CONSTEXPR unsigned char uchar_values[] =
      {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
       255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-      255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+      255, 255, 255, 255, 255, 255, 255, 254, 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,
@@ -47,7 +47,7 @@ static_assert(sizeof(uchar_values) == 256, "uchar_values should represent all 25
 
 #endif // __NVCC__
 
-// Convert characters for 0-9, A-Z, a-z to 0-35. Anything else is 255
+// Convert characters for 0-9, A-Z, a-z to 0-35. The digit separator ' is 254. Anything else is 255
 BOOST_INT128_HOST_DEVICE BOOST_INT128_FORCE_INLINE constexpr auto digit_from_char(char val) noexcept -> unsigned char
 {
     #if defined(BOOST_INT128_HAS_GPU_SUPPORT)
@@ -55,7 +55,7 @@ BOOST_INT128_HOST_DEVICE BOOST_INT128_FORCE_INLINE constexpr auto digit_from_cha
     constexpr unsigned char uchar_values[] =
     {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
      255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-     255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+     255, 255, 255, 255, 255, 255, 255, 254, 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,
@@ -77,10 +77,10 @@ BOOST_INT128_HOST_DEVICE BOOST_INT128_FORCE_INLINE constexpr auto digit_from_cha
     return uchar_values[static_cast<unsigned char>(val)];
 }
 
-template <typename Integer, typename Unsigned_Integer>
+template <typename Integer, typename Unsigned_Integer, bool is_literal_parse = false>
 BOOST_INT128_HOST_DEVICE constexpr int from_chars_integer_impl(const char* first, const char* last, Integer& value, int base) noexcept
 {
-    if (first >= last)
+    if (last - first <= 0)
     {
         return EINVAL;
     }
@@ -152,7 +152,19 @@ BOOST_INT128_HOST_DEVICE constexpr int from_chars_integer_impl(const char* first
 
     for (; i < fast_limit; ++i)
     {
-        const auto current_digit = static_cast<Unsigned_Integer>(digit_from_char(*next));
+        const auto raw_digit = digit_from_char(*next);
+
+        // When parsing a user-defined literal skip the digit separator ' (marked as 254)
+        BOOST_INT128_IF_CONSTEXPR (is_literal_parse)
+        {
+            if (raw_digit == 254)
+            {
+                ++next;
+                continue;
+            }
+        }
+
+        const auto current_digit = static_cast<Unsigned_Integer>(raw_digit);
 
         if (current_digit >= unsigned_base)
         {
@@ -165,7 +177,19 @@ BOOST_INT128_HOST_DEVICE constexpr int from_chars_integer_impl(const char* first
 
     for (; i < nc; ++i)
     {
-        const auto current_digit = static_cast<Unsigned_Integer>(digit_from_char(*next));
+        const auto raw_digit = digit_from_char(*next);
+
+        // When parsing a user-defined literal skip the digit separator ' (marked as 254)
+        BOOST_INT128_IF_CONSTEXPR (is_literal_parse)
+        {
+            if (raw_digit == 254)
+            {
+                ++next;
+                continue;
+            }
+        }
+
+        const auto current_digit = static_cast<Unsigned_Integer>(raw_digit);
 
         if (current_digit >= unsigned_base)
         {
@@ -229,6 +253,18 @@ BOOST_INT128_TEST_EXPORT BOOST_INT128_HOST_DEVICE constexpr int from_chars(const
     return impl::from_chars_integer_impl<int128_t, uint128_t>(first, last, value, base);
 }
 
+// Parsing entry points for the user-defined literals. Unlike from_chars these skip the
+// C++ digit separator ' so that literals such as 1'234'567_u128 are accepted.
+BOOST_INT128_TEST_EXPORT BOOST_INT128_HOST_DEVICE constexpr int from_chars_literal(const char* first, const char* last, uint128_t& value, int base = 10) noexcept
+{
+    return impl::from_chars_integer_impl<uint128_t, uint128_t, true>(first, last, value, base);
+}
+
+BOOST_INT128_TEST_EXPORT BOOST_INT128_HOST_DEVICE constexpr int from_chars_literal(const char* first, const char* last, int128_t& value, int base = 10) noexcept
+{
+    return impl::from_chars_integer_impl<int128_t, uint128_t, true>(first, last, value, base);
+}
+
 } // namespace detail
 } // namespace int128
 } // namespace boost
diff --git a/include/boost/int128/literals.hpp b/include/boost/int128/literals.hpp
index 3d388f26..e170f7db 100644
--- a/include/boost/int128/literals.hpp
+++ b/include/boost/int128/literals.hpp
@@ -18,56 +18,56 @@ namespace literals {
 BOOST_INT128_EXPORT BOOST_INT128_HOST_DEVICE constexpr uint128_t operator ""_u128(const char* str) noexcept
 {
     uint128_t result {};
-    detail::from_chars(str, str + detail::strlen(str), result);
+    detail::from_chars_literal(str, str + detail::strlen(str), result);
     return result;
 }
 
 BOOST_INT128_EXPORT BOOST_INT128_HOST_DEVICE constexpr uint128_t operator ""_U128(const char* str) noexcept
 {
     uint128_t result {};
-    detail::from_chars(str, str + detail::strlen(str), result);
+    detail::from_chars_literal(str, str + detail::strlen(str), result);
     return result;
 }
 
 BOOST_INT128_EXPORT BOOST_INT128_HOST_DEVICE constexpr uint128_t operator ""_u128(const char* str, std::size_t len) noexcept
 {
     uint128_t result {};
-    detail::from_chars(str, str + len, result);
+    detail::from_chars_literal(str, str + len, result);
     return result;
 }
 
 BOOST_INT128_EXPORT BOOST_INT128_HOST_DEVICE constexpr uint128_t operator ""_U128(const char* str, std::size_t len) noexcept
 {
     uint128_t result {};
-    detail::from_chars(str, str + len, result);
+    detail::from_chars_literal(str, str + len, result);
     return result;
 }
 
 BOOST_INT128_EXPORT BOOST_INT128_HOST_DEVICE constexpr int128_t operator ""_i128(const char* str) noexcept
 {
     int128_t result {};
-    detail::from_chars(str, str + detail::strlen(str), result);
+    detail::from_chars_literal(str, str + detail::strlen(str), result);
     return result;
 }
 
 BOOST_INT128_EXPORT BOOST_INT128_HOST_DEVICE constexpr int128_t operator ""_I128(const char* str) noexcept
 {
     int128_t result {};
-    detail::from_chars(str, str + detail::strlen(str), result);
+    detail::from_chars_literal(str, str + detail::strlen(str), result);
     return result;
 }
 
 BOOST_INT128_EXPORT BOOST_INT128_HOST_DEVICE constexpr int128_t operator ""_i128(const char* str, std::size_t len) noexcept
 {
     int128_t result {};
-    detail::from_chars(str, str + len, result);
+    detail::from_chars_literal(str, str + len, result);
     return result;
 }
 
 BOOST_INT128_EXPORT BOOST_INT128_HOST_DEVICE constexpr int128_t operator ""_I128(const char* str, std::size_t len) noexcept
 {
     int128_t result {};
-    detail::from_chars(str, str + len, result);
+    detail::from_chars_literal(str, str + len, result);
     return result;
 }
 
diff --git a/test/test_literals.cpp b/test/test_literals.cpp
index 2e61254d..fe55ad83 100644
--- a/test/test_literals.cpp
+++ b/test/test_literals.cpp
@@ -32,6 +32,34 @@ void test_u128_literals()
     BOOST_TEST(max_val == macro_val);
 }
 
+// Warning with only MSVC 14.1
+#ifdef _MSC_VER
+#  pragma warning(push)
+#  pragma warning(disable: 4307)
+#endif
+
+void test_u128_digit_separators()
+{
+    // C++ digit separators (') are ignored inside numeric literals
+    BOOST_TEST(boost::int128::uint128_t{1234567} == 1'234'567_u128);
+    BOOST_TEST(boost::int128::uint128_t{1000} == 1'000_U128);
+    BOOST_TEST(boost::int128::uint128_t{1234} == 12'34_u128);
+
+    // Separators are also honored through the convenience macro
+    BOOST_TEST(boost::int128::uint128_t{1234} == BOOST_INT128_UINT128_C(1'234));
+
+    // The string form of the literal skips separators as well
+    BOOST_TEST(boost::int128::uint128_t{1234} == "1'234"_u128);
+    BOOST_TEST(boost::int128::uint128_t{1234} == "1'234"_U128);
+
+    // Full-width value with a separator between every group of three digits
+    const boost::int128::uint128_t max_val {std::numeric_limits<boost::int128::uint128_t>::max()};
+    BOOST_TEST(max_val == 340'282'366'920'938'463'463'374'607'431'768'211'455_u128);
+
+    // Separators must be usable in a constant expression
+    static_assert(100'000_u128 == boost::int128::uint128_t{100000}, "constexpr separator");
+}
+
 void test_i128_literals()
 {
     BOOST_TEST(boost::int128::int128_t{0} == 0_i128);
@@ -49,10 +77,40 @@ void test_i128_literals()
     BOOST_TEST("-42"_i128 == -42);
 }
 
+void test_i128_digit_separators()
+{
+    // C++ digit separators (') are ignored inside numeric literals
+    BOOST_TEST(boost::int128::int128_t{1000} == 1'000_i128);
+    BOOST_TEST(boost::int128::int128_t{9999} == 9'999_I128);
+
+    // A leading unary minus is applied after the (separated) literal is parsed
+    BOOST_TEST(boost::int128::int128_t{-1000000} == -1'000'000_i128);
+
+    // Separators are also honored through the convenience macro
+    BOOST_TEST(boost::int128::int128_t{9999} == BOOST_INT128_INT128_C(9'999));
+
+    // The string form of the literal skips separators as well
+    BOOST_TEST(boost::int128::int128_t{1234} == "1'234"_i128);
+    BOOST_TEST(boost::int128::int128_t{1234} == "1'234"_I128);
+
+    // Full-width value with a separator between every group of three digits
+    const boost::int128::int128_t max_val {std::numeric_limits<boost::int128::int128_t>::max()};
+    BOOST_TEST(max_val == 170'141'183'460'469'231'731'687'303'715'884'105'727_i128);
+
+    // Separators must be usable in a constant expression
+    static_assert(100'000_i128 == boost::int128::int128_t{100000}, "constexpr separator");
+}
+
+#ifdef _MSC_VER
+#  pragma warning(pop)
+#endif
+
 int main()
 {
     test_u128_literals();
+    test_u128_digit_separators();
     test_i128_literals();
+    test_i128_digit_separators();
 
     return boost::report_errors();
 }