diff --git a/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.h b/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.h
--- a/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.h
+++ b/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.h
@@ -49,6 +49,10 @@
   bool isBitFieldWidth(const clang::ast_matchers::MatchFinder::MatchResult &Result,
                        const IntegerLiteral &Literal) const;
 
+  bool isUserDefinedLiteral(
+      const clang::ast_matchers::MatchFinder::MatchResult &Result,
+      const clang::Expr &Literal) const;
+
   template <typename L>
   void checkBoundMatch(const ast_matchers::MatchFinder::MatchResult &Result,
                        const char *BoundName) {
@@ -72,6 +76,10 @@
     if (isBitFieldWidth(Result, *MatchedLiteral))
       return;
 
+    if (IgnoreUserDefinedLiterals &&
+        isUserDefinedLiteral(Result, *MatchedLiteral))
+      return;
+
     const StringRef LiteralSourceText = Lexer::getSourceText(
         CharSourceRange::getTokenRange(MatchedLiteral->getSourceRange()),
         *Result.SourceManager, getLangOpts());
@@ -85,6 +93,7 @@
   const bool IgnoreBitFieldsWidths;
   const bool IgnorePowersOf2IntegerValues;
   const bool IgnoreTypeAliases;
+  const bool IgnoreUserDefinedLiterals;
   const StringRef RawIgnoredIntegerValues;
   const StringRef RawIgnoredFloatingPointValues;
 
diff --git a/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp b/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp
@@ -81,6 +81,8 @@
       IgnorePowersOf2IntegerValues(
           Options.get("IgnorePowersOf2IntegerValues", false)),
       IgnoreTypeAliases(Options.get("IgnoreTypeAliases", false)),
+      IgnoreUserDefinedLiterals(
+          Options.get("IgnoreUserDefinedLiterals", false)),
       RawIgnoredIntegerValues(
           Options.get("IgnoredIntegerValues", DefaultIgnoredIntegerValues)),
       RawIgnoredFloatingPointValues(Options.get(
@@ -130,6 +132,7 @@
   Options.store(Opts, "IgnorePowersOf2IntegerValues",
                 IgnorePowersOf2IntegerValues);
   Options.store(Opts, "IgnoreTypeAliases", IgnoreTypeAliases);
+  Options.store(Opts, "IgnoreUserDefinedLiterals", IgnoreUserDefinedLiterals);
   Options.store(Opts, "IgnoredIntegerValues", RawIgnoredIntegerValues);
   Options.store(Opts, "IgnoredFloatingPointValues",
                 RawIgnoredFloatingPointValues);
@@ -243,5 +246,14 @@
                       });
 }
 
+bool MagicNumbersCheck::isUserDefinedLiteral(
+    const clang::ast_matchers::MatchFinder::MatchResult &Result,
+    const clang::Expr &Literal) const {
+  DynTypedNodeList Parents = Result.Context->getParents(Literal);
+  if (Parents.empty())
+    return false;
+  return Parents[0].get<UserDefinedLiteral>() != nullptr;
+}
+
 } // namespace tidy::readability
 } // namespace clang
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -211,6 +211,9 @@
   behavior of using `i` as the prefix for enum tags, set the `EnumConstantPrefix`
   option to `i` instead of using `EnumConstantHungarianPrefix`.
 
+- Added support to optionally ignore user-defined literals in
+  :doc:`readability-magic-numbers<clang-tidy/checks/readability/magic-numbers>`.
+
 - Fixed a false positive in :doc:`readability-container-size-empty
   <clang-tidy/checks/readability/container-size-empty>` check when comparing
   ``std::array`` objects to default constructed ones. The behavior for this and
diff --git a/clang-tools-extra/docs/clang-tidy/checks/readability/magic-numbers.rst b/clang-tools-extra/docs/clang-tidy/checks/readability/magic-numbers.rst
--- a/clang-tools-extra/docs/clang-tidy/checks/readability/magic-numbers.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/readability/magic-numbers.rst
@@ -57,7 +57,7 @@
 
    const size_t NUMBER_OF_ELEMENTS = 30;
    using containerType = CustomType<int, NUMBER_OF_ELEMENTS>;
-   
+
    struct OtherType {
       containerType container;
    }
@@ -144,3 +144,8 @@
 
    Boolean value indicating whether to accept magic numbers in ``typedef`` or
    ``using`` declarations. Default value is `false`.
+
+.. option:: IgnoreUserDefinedLiterals
+
+   Boolean value indicating whether to accept magic numbers in user-defined
+   literals. Default value is `false`.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/readability/magic-numbers-userliteral.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/magic-numbers-userliteral.cpp
--- a/clang-tools-extra/test/clang-tidy/checkers/readability/magic-numbers-userliteral.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/magic-numbers-userliteral.cpp
@@ -1,10 +1,18 @@
-// RUN: %check_clang_tidy -std=c++14-or-later %s readability-magic-numbers %t --
+// RUN: %check_clang_tidy -check-suffixes=UDL-ALLOWED -std=c++14-or-later %s readability-magic-numbers %t \
+// RUN: -config='{CheckOptions: \
+// RUN:  [{key: readability-magic-numbers.IgnoreUserDefinedLiterals, value: false}]}' \
+// RUN: --
+// RUN: %check_clang_tidy -check-suffixes=UDL-IGNORED -std=c++14-or-later %s readability-magic-numbers %t \
+// RUN: -config='{CheckOptions: \
+// RUN:  [{key: readability-magic-numbers.IgnoreUserDefinedLiterals, value: true}]}' \
+// RUN: --
 
 namespace std {
   class string {};
   using size_t = decltype(sizeof(int));
   string operator ""s(const char *, std::size_t);
   int operator "" s(unsigned long long);
+  float operator "" s(long double);
 }
 
 void UserDefinedLiteral() {
@@ -12,5 +20,9 @@
   "Hello World"s;
   const int i = 3600s;
   int j = 3600s;
-  // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: 3600s is a magic number; consider replacing it with a named constant [readability-magic-numbers]
+  // CHECK-MESSAGES-UDL-ALLOWED: :[[@LINE-1]]:11: warning: 3600s is a magic number; consider replacing it with a named constant [readability-magic-numbers]
+  // CHECK-MESSAGES-UDL-IGNORED-NOT: :[[@LINE-2]]:11: warning: 3600s is a magic number; consider replacing it with a named constant [readability-magic-numbers]
+  float k = 3600.0s;
+  // CHECK-MESSAGES-UDL-ALLOWED: :[[@LINE-1]]:13: warning: 3600.0s is a magic number; consider replacing it with a named constant [readability-magic-numbers]
+  // CHECK-MESSAGES-UDL-IGNORED-NOT: :[[@LINE-1]]:13: warning: 3600.0s is a magic number; consider replacing it with a named constant [readability-magic-numbers]
 }