diff --git a/include/nlohmann/detail/boolean_operators.hpp b/include/nlohmann/detail/boolean_operators.hpp
new file mode 100644
index 00000000..06335866
--- /dev/null
+++ b/include/nlohmann/detail/boolean_operators.hpp
@@ -0,0 +1,8 @@
+#pragma once
+
+// Header <ciso646> is removed in C++20.
+// See <https://github.com/nlohmann/json/issues/2089> for more information.
+
+#if __cplusplus <= 201703L
+    #include <ciso646> // and, not, or
+#endif
diff --git a/include/nlohmann/detail/conversions/from_json.hpp b/include/nlohmann/detail/conversions/from_json.hpp
index c389dca7..d6e02798 100644
--- a/include/nlohmann/detail/conversions/from_json.hpp
+++ b/include/nlohmann/detail/conversions/from_json.hpp
@@ -2,7 +2,6 @@
 
 #include <algorithm> // transform
 #include <array> // array
-#include <ciso646> // and, not
 #include <forward_list> // forward_list
 #include <iterator> // inserter, front_inserter, end
 #include <map> // map
@@ -13,6 +12,7 @@
 #include <utility> // pair, declval
 #include <valarray> // valarray
 
+#include <nlohmann/detail/boolean_operators.hpp>
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/meta/cpp_future.hpp>
diff --git a/include/nlohmann/detail/conversions/to_chars.hpp b/include/nlohmann/detail/conversions/to_chars.hpp
index aed587cc..5851fd0a 100644
--- a/include/nlohmann/detail/conversions/to_chars.hpp
+++ b/include/nlohmann/detail/conversions/to_chars.hpp
@@ -2,12 +2,13 @@
 
 #include <array> // array
 #include <cassert> // assert
-#include <ciso646> // or, and, not
 #include <cmath>   // signbit, isfinite
 #include <cstdint> // intN_t, uintN_t
 #include <cstring> // memcpy, memmove
 #include <limits> // numeric_limits
 #include <type_traits> // conditional
+
+#include <nlohmann/detail/boolean_operators.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 
 namespace nlohmann
diff --git a/include/nlohmann/detail/conversions/to_json.hpp b/include/nlohmann/detail/conversions/to_json.hpp
index 10b21d16..7ff1b282 100644
--- a/include/nlohmann/detail/conversions/to_json.hpp
+++ b/include/nlohmann/detail/conversions/to_json.hpp
@@ -1,7 +1,6 @@
 #pragma once
 
 #include <algorithm> // copy
-#include <ciso646> // or, and, not
 #include <iterator> // begin, end
 #include <string> // string
 #include <tuple> // tuple, get
@@ -10,6 +9,7 @@
 #include <valarray> // valarray
 #include <vector> // vector
 
+#include <nlohmann/detail/boolean_operators.hpp>
 #include <nlohmann/detail/iterators/iteration_proxy.hpp>
 #include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/meta/type_traits.hpp>
diff --git a/include/nlohmann/detail/iterators/iter_impl.hpp b/include/nlohmann/detail/iterators/iter_impl.hpp
index 3a362971..0b79202a 100644
--- a/include/nlohmann/detail/iterators/iter_impl.hpp
+++ b/include/nlohmann/detail/iterators/iter_impl.hpp
@@ -1,9 +1,9 @@
 #pragma once
 
-#include <ciso646> // not
 #include <iterator> // iterator, random_access_iterator_tag, bidirectional_iterator_tag, advance, next
 #include <type_traits> // conditional, is_const, remove_const
 
+#include <nlohmann/detail/boolean_operators.hpp>
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/iterators/internal_iterator.hpp>
 #include <nlohmann/detail/iterators/primitive_iterator.hpp>
diff --git a/include/nlohmann/detail/meta/cpp_future.hpp b/include/nlohmann/detail/meta/cpp_future.hpp
index 948cd4fb..11f88acc 100644
--- a/include/nlohmann/detail/meta/cpp_future.hpp
+++ b/include/nlohmann/detail/meta/cpp_future.hpp
@@ -1,9 +1,10 @@
 #pragma once
 
-#include <ciso646> // not
 #include <cstddef> // size_t
 #include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
 
+#include <nlohmann/detail/boolean_operators.hpp>
+
 namespace nlohmann
 {
 namespace detail
diff --git a/include/nlohmann/detail/meta/type_traits.hpp b/include/nlohmann/detail/meta/type_traits.hpp
index 13e92cb4..3b93fa8b 100644
--- a/include/nlohmann/detail/meta/type_traits.hpp
+++ b/include/nlohmann/detail/meta/type_traits.hpp
@@ -1,10 +1,10 @@
 #pragma once
 
-#include <ciso646> // not
 #include <limits> // numeric_limits
 #include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
 #include <utility> // declval
 
+#include <nlohmann/detail/boolean_operators.hpp>
 #include <nlohmann/detail/iterators/iterator_traits.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/meta/cpp_future.hpp>
diff --git a/include/nlohmann/detail/output/serializer.hpp b/include/nlohmann/detail/output/serializer.hpp
index da544fad..75ce6783 100644
--- a/include/nlohmann/detail/output/serializer.hpp
+++ b/include/nlohmann/detail/output/serializer.hpp
@@ -3,7 +3,6 @@
 #include <algorithm> // reverse, remove, fill, find, none_of
 #include <array> // array
 #include <cassert> // assert
-#include <ciso646> // and, or
 #include <clocale> // localeconv, lconv
 #include <cmath> // labs, isfinite, isnan, signbit
 #include <cstddef> // size_t, ptrdiff_t
@@ -14,6 +13,7 @@
 #include <type_traits> // is_same
 #include <utility> // move
 
+#include <nlohmann/detail/boolean_operators.hpp>
 #include <nlohmann/detail/conversions/to_chars.hpp>
 #include <nlohmann/detail/exceptions.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
diff --git a/include/nlohmann/detail/value_t.hpp b/include/nlohmann/detail/value_t.hpp
index 86b4630b..7580d856 100644
--- a/include/nlohmann/detail/value_t.hpp
+++ b/include/nlohmann/detail/value_t.hpp
@@ -1,11 +1,12 @@
 #pragma once
 
 #include <array> // array
-#include <ciso646> // and
 #include <cstddef> // size_t
 #include <cstdint> // uint8_t
 #include <string> // string
 
+#include <nlohmann/detail/boolean_operators.hpp>
+
 namespace nlohmann
 {
 namespace detail
diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index ff5accfd..6c616faa 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -36,7 +36,6 @@ SOFTWARE.
 
 #include <algorithm> // all_of, find, for_each
 #include <cassert> // assert
-#include <ciso646> // and, not, or
 #include <cstddef> // nullptr_t, ptrdiff_t, size_t
 #include <functional> // hash, less
 #include <initializer_list> // initializer_list
@@ -49,6 +48,7 @@ SOFTWARE.
 #include <vector> // vector
 
 #include <nlohmann/adl_serializer.hpp>
+#include <nlohmann/detail/boolean_operators.hpp>
 #include <nlohmann/detail/conversions/from_json.hpp>
 #include <nlohmann/detail/conversions/to_json.hpp>
 #include <nlohmann/detail/exceptions.hpp>
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index c5ef3f7f..7b8cbb7f 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -36,7 +36,6 @@ SOFTWARE.
 
 #include <algorithm> // all_of, find, for_each
 #include <cassert> // assert
-#include <ciso646> // and, not, or
 #include <cstddef> // nullptr_t, ptrdiff_t, size_t
 #include <functional> // hash, less
 #include <initializer_list> // initializer_list
@@ -58,7 +57,6 @@ SOFTWARE.
 
 #include <algorithm> // transform
 #include <array> // array
-#include <ciso646> // and, not
 #include <forward_list> // forward_list
 #include <iterator> // inserter, front_inserter, end
 #include <map> // map
@@ -69,6 +67,16 @@ SOFTWARE.
 #include <utility> // pair, declval
 #include <valarray> // valarray
 
+// #include <nlohmann/detail/boolean_operators.hpp>
+
+
+// Header <ciso646> is removed in C++20.
+// See <https://github.com/nlohmann/json/issues/2089> for more information.
+
+#if __cplusplus <= 201703L
+    #include <ciso646> // and, not, or
+#endif
+
 // #include <nlohmann/detail/exceptions.hpp>
 
 
@@ -2495,10 +2503,12 @@ class other_error : public exception
 // #include <nlohmann/detail/meta/cpp_future.hpp>
 
 
-#include <ciso646> // not
 #include <cstddef> // size_t
 #include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
 
+// #include <nlohmann/detail/boolean_operators.hpp>
+
+
 namespace nlohmann
 {
 namespace detail
@@ -2560,11 +2570,12 @@ constexpr T static_const<T>::value;
 // #include <nlohmann/detail/meta/type_traits.hpp>
 
 
-#include <ciso646> // not
 #include <limits> // numeric_limits
 #include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
 #include <utility> // declval
 
+// #include <nlohmann/detail/boolean_operators.hpp>
+
 // #include <nlohmann/detail/iterators/iterator_traits.hpp>
 
 
@@ -3145,11 +3156,13 @@ struct is_constructible_tuple<T1, std::tuple<Args...>> : conjunction<std::is_con
 
 
 #include <array> // array
-#include <ciso646> // and
 #include <cstddef> // size_t
 #include <cstdint> // uint8_t
 #include <string> // string
 
+// #include <nlohmann/detail/boolean_operators.hpp>
+
+
 namespace nlohmann
 {
 namespace detail
@@ -3599,7 +3612,6 @@ constexpr const auto& from_json = detail::static_const<detail::from_json_fn>::va
 
 
 #include <algorithm> // copy
-#include <ciso646> // or, and, not
 #include <iterator> // begin, end
 #include <string> // string
 #include <tuple> // tuple, get
@@ -3608,6 +3620,8 @@ constexpr const auto& from_json = detail::static_const<detail::from_json_fn>::va
 #include <valarray> // valarray
 #include <vector> // vector
 
+// #include <nlohmann/detail/boolean_operators.hpp>
+
 // #include <nlohmann/detail/iterators/iteration_proxy.hpp>
 
 
@@ -4192,6 +4206,8 @@ struct adl_serializer
 
 }  // namespace nlohmann
 
+// #include <nlohmann/detail/boolean_operators.hpp>
+
 // #include <nlohmann/detail/conversions/from_json.hpp>
 
 // #include <nlohmann/detail/conversions/to_json.hpp>
@@ -10041,10 +10057,11 @@ template<typename BasicJsonType> struct internal_iterator
 // #include <nlohmann/detail/iterators/iter_impl.hpp>
 
 
-#include <ciso646> // not
 #include <iterator> // iterator, random_access_iterator_tag, bidirectional_iterator_tag, advance, next
 #include <type_traits> // conditional, is_const, remove_const
 
+// #include <nlohmann/detail/boolean_operators.hpp>
+
 // #include <nlohmann/detail/exceptions.hpp>
 
 // #include <nlohmann/detail/iterators/internal_iterator.hpp>
@@ -13576,7 +13593,6 @@ class binary_writer
 #include <algorithm> // reverse, remove, fill, find, none_of
 #include <array> // array
 #include <cassert> // assert
-#include <ciso646> // and, or
 #include <clocale> // localeconv, lconv
 #include <cmath> // labs, isfinite, isnan, signbit
 #include <cstddef> // size_t, ptrdiff_t
@@ -13587,17 +13603,21 @@ class binary_writer
 #include <type_traits> // is_same
 #include <utility> // move
 
+// #include <nlohmann/detail/boolean_operators.hpp>
+
 // #include <nlohmann/detail/conversions/to_chars.hpp>
 
 
 #include <array> // array
 #include <cassert> // assert
-#include <ciso646> // or, and, not
 #include <cmath>   // signbit, isfinite
 #include <cstdint> // intN_t, uintN_t
 #include <cstring> // memcpy, memmove
 #include <limits> // numeric_limits
 #include <type_traits> // conditional
+
+// #include <nlohmann/detail/boolean_operators.hpp>
+
 // #include <nlohmann/detail/macro_scope.hpp>