diff --git a/docs/mkdocs/docs/api/macros/json_use_legacy_discarded_value_comparison.md b/docs/mkdocs/docs/api/macros/json_use_legacy_discarded_value_comparison.md
index b6efd8dbd..e61ce1a3e 100644
--- a/docs/mkdocs/docs/api/macros/json_use_legacy_discarded_value_comparison.md
+++ b/docs/mkdocs/docs/api/macros/json_use_legacy_discarded_value_comparison.md
@@ -81,3 +81,6 @@ When the macro is not defined, the library will define it to its default value.
 ## Version history
 
 - Added in version 3.11.0.
+- Fixed in version 3.13.0 so `<=` and `>=` also emulate the legacy behavior in C++20 when the JSON value is the
+  right-hand operand of a scalar comparison; before, only the 3-way-comparison-rewritten candidate was found, which
+  yielded `#!cpp false` instead of `#!cpp true`.
diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index 1ff12c7f3..b802b4b59 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -4939,6 +4939,27 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     {
         return *this >= basic_json(rhs);
     }
+
+    // a scalar on the left-hand side would otherwise select the candidate
+    // rewritten from operator<=>, which does not emulate the legacy behavior
+
+    /// @brief comparison: less than or equal
+    /// @sa https://json.nlohmann.me/api/basic_json/operator_le/
+    template<typename ScalarType>
+    requires std::is_scalar_v<ScalarType>
+    friend bool operator<=(ScalarType lhs, const_reference rhs) noexcept
+    {
+        return basic_json(lhs) <= rhs;
+    }
+
+    /// @brief comparison: greater than or equal
+    /// @sa https://json.nlohmann.me/api/basic_json/operator_ge/
+    template<typename ScalarType>
+    requires std::is_scalar_v<ScalarType>
+    friend bool operator>=(ScalarType lhs, const_reference rhs) noexcept
+    {
+        return basic_json(lhs) >= rhs;
+    }
 #endif
 #else
     /// @brief comparison: equal
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 9e27f62f0..2adc9978f 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -31644,6 +31644,27 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     {
         return *this >= basic_json(rhs);
     }
+
+    // a scalar on the left-hand side would otherwise select the candidate
+    // rewritten from operator<=>, which does not emulate the legacy behavior
+
+    /// @brief comparison: less than or equal
+    /// @sa https://json.nlohmann.me/api/basic_json/operator_le/
+    template<typename ScalarType>
+    requires std::is_scalar_v<ScalarType>
+    friend bool operator<=(ScalarType lhs, const_reference rhs) noexcept
+    {
+        return basic_json(lhs) <= rhs;
+    }
+
+    /// @brief comparison: greater than or equal
+    /// @sa https://json.nlohmann.me/api/basic_json/operator_ge/
+    template<typename ScalarType>
+    requires std::is_scalar_v<ScalarType>
+    friend bool operator>=(ScalarType lhs, const_reference rhs) noexcept
+    {
+        return basic_json(lhs) >= rhs;
+    }
 #endif
 #else
     /// @brief comparison: equal
diff --git a/tests/src/unit-comparison.cpp b/tests/src/unit-comparison.cpp
index febfd9b42..a65d5c1b3 100644
--- a/tests/src/unit-comparison.cpp
+++ b/tests/src/unit-comparison.cpp
@@ -750,6 +750,28 @@ TEST_CASE("regression #3868 - heterogeneous comparisons compile under C++20 (P24
         CHECK_FALSE(j != i);
     }
 }
+
+#if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+TEST_CASE("regression #5665 - scalar <= discarded and scalar >= discarded in C++20 legacy mode")
+{
+    // Issue #5665: with a scalar on the left-hand side, <= and >= only had the
+    // candidate rewritten from operator<=>, which does not emulate the legacy
+    // discarded-value behavior. Check that scalar-on-the-left now matches the
+    // other three operand orders.
+    const json discarded(json::value_t::discarded);
+    const json one = 1;
+
+    CHECK(discarded <= 1);
+    CHECK(discarded >= 1);
+    CHECK(one <= discarded);
+    CHECK(one >= discarded);
+    CHECK(1 <= discarded);
+    CHECK(1 >= discarded);
+    CHECK(1.5 <= discarded);
+    CHECK(1.5 >= discarded);
+}
+#endif
+
 #endif
 
 namespace