diff --git a/docs/CommandGuide/FileCheck.rst b/docs/CommandGuide/FileCheck.rst
index e8b324d080d..0072c9c0347 100644
--- a/docs/CommandGuide/FileCheck.rst
+++ b/docs/CommandGuide/FileCheck.rst
@@ -71,6 +71,11 @@ and from the command line.
  The :option:`--strict-whitespace` argument disables this behavior. End-of-line
  sequences are canonicalized to UNIX-style ``\n`` in all modes.
 
+.. option:: --ignore-case
+
+  By default, FileCheck uses case-sensitive matching. This option causes
+  FileCheck to use case-insensitive matching.
+
 .. option:: --implicit-check-not check-pattern
 
   Adds implicit negative checks for the specified patterns between positive
diff --git a/include/llvm/Support/FileCheck.h b/include/llvm/Support/FileCheck.h
index 5c6585ed76f..2547449246a 100644
--- a/include/llvm/Support/FileCheck.h
+++ b/include/llvm/Support/FileCheck.h
@@ -30,6 +30,7 @@ struct FileCheckRequest {
   std::vector<std::string> GlobalDefines;
   bool AllowEmptyInput = false;
   bool MatchFullLines = false;
+  bool IgnoreCase = false;
   bool EnableVarScope = false;
   bool AllowDeprecatedDagOverlap = false;
   bool Verbose = false;
diff --git a/lib/Support/FileCheck.cpp b/lib/Support/FileCheck.cpp
index c3f537b3524..841e406a7b6 100644
--- a/lib/Support/FileCheck.cpp
+++ b/lib/Support/FileCheck.cpp
@@ -320,6 +320,7 @@ bool FileCheckPattern::parsePattern(StringRef PatternStr, StringRef Prefix,
                                     SourceMgr &SM,
                                     const FileCheckRequest &Req) {
   bool MatchFullLinesHere = Req.MatchFullLines && CheckTy != Check::CheckNot;
+  IgnoreCase = Req.IgnoreCase;
 
   PatternLoc = SMLoc::getFromPointer(PatternStr.data());
 
@@ -619,7 +620,8 @@ Expected<size_t> FileCheckPattern::match(StringRef Buffer, size_t &MatchLen,
   // If this is a fixed string pattern, just match it now.
   if (!FixedStr.empty()) {
     MatchLen = FixedStr.size();
-    size_t Pos = Buffer.find(FixedStr);
+    size_t Pos = IgnoreCase ? Buffer.find_lower(FixedStr)
+                            : Buffer.find(FixedStr);
     if (Pos == StringRef::npos)
       return make_error<FileCheckNotFoundError>();
     return Pos;
@@ -657,7 +659,10 @@ Expected<size_t> FileCheckPattern::match(StringRef Buffer, size_t &MatchLen,
   }
 
   SmallVector<StringRef, 4> MatchInfo;
-  if (!Regex(RegExToMatch, Regex::Newline).match(Buffer, &MatchInfo))
+  unsigned int Flags = Regex::Newline;
+  if (IgnoreCase)
+    Flags |= Regex::IgnoreCase;
+  if (!Regex(RegExToMatch, Flags).match(Buffer, &MatchInfo))
     return make_error<FileCheckNotFoundError>();
 
   // Successful regex match.
diff --git a/lib/Support/FileCheckImpl.h b/lib/Support/FileCheckImpl.h
index 001b3589d5f..06ce8301cec 100644
--- a/lib/Support/FileCheckImpl.h
+++ b/lib/Support/FileCheckImpl.h
@@ -428,6 +428,9 @@ class FileCheckPattern {
   /// line to the one with this CHECK.
   Optional<size_t> LineNumber;
 
+  /// Ignore case while matching if set to true.
+  bool IgnoreCase = false;
+
 public:
   FileCheckPattern(Check::FileCheckType Ty, FileCheckPatternContext *Context,
                    Optional<size_t> Line = None)
diff --git a/test/FileCheck/check-ignore-case.txt b/test/FileCheck/check-ignore-case.txt
new file mode 100644
index 00000000000..6a42a52fc44
--- /dev/null
+++ b/test/FileCheck/check-ignore-case.txt
@@ -0,0 +1,45 @@
+## Check that a full line is matched case insensitively.
+# RUN: FileCheck --ignore-case --match-full-lines --check-prefix=FULL --input-file=%s %s
+
+## Check that a regular expression matches case insensitively.
+# RUN: FileCheck --ignore-case --check-prefix=REGEX --input-file=%s %s
+
+## Check that a pattern from command line matches case insensitively.
+# RUN: FileCheck --ignore-case --check-prefix=PAT --DPATTERN="THIS is the" --input-file=%s %s
+
+## Check that COUNT and NEXT work case insensitively.
+# RUN: FileCheck --ignore-case --check-prefix=CNT --input-file=%s %s
+
+## Check that match on same line works case insensitively.
+# RUN: FileCheck --ignore-case --check-prefix=LINE --input-file=%s %s
+
+## Check that option --implicit-not works case insensitively.
+# RUN: sed '/^#/d' %s | FileCheck --implicit-check-not=sTrInG %s
+# RUN: sed '/^#/d' %s | not FileCheck --ignore-case --implicit-check-not=sTrInG %s 2>&1 | FileCheck --check-prefix=ERROR %s
+
+this is the STRING to be matched
+
+# FULL: tHis iS The String TO be matched
+# REGEX: s{{TRing}}
+# PAT: [[PATTERN]] string
+
+Loop 1
+lOop 2
+loOp 3
+looP 4
+loop 5
+LOOP 6
+BREAK
+
+# CNT-COUNT-6: LOop {{[0-9]}}
+# CNT-NOT: loop
+# CNT-NEXT: break
+
+One Line To Match
+
+# LINE: {{o}}ne line
+# LINE-SAME: {{t}}o match
+
+# ERROR: command line:1:{{[0-9]+}}: error: CHECK-NOT: excluded string found in input
+# ERROR-NEXT: -implicit-check-not='sTrInG'
+# ERROR: note: found here
diff --git a/utils/FileCheck/FileCheck.cpp b/utils/FileCheck/FileCheck.cpp
index 8718be28ac9..44d5be13751 100644
--- a/utils/FileCheck/FileCheck.cpp
+++ b/utils/FileCheck/FileCheck.cpp
@@ -48,6 +48,10 @@ static cl::opt<bool> NoCanonicalizeWhiteSpace(
     "strict-whitespace",
     cl::desc("Do not treat all horizontal whitespace as equivalent"));
 
+static cl::opt<bool> IgnoreCase(
+    "ignore-case",
+    cl::desc("Use case-insensitive matching"));
+
 static cl::list<std::string> ImplicitCheckNot(
     "implicit-check-not",
     cl::desc("Add an implicit negative check with this pattern to every\n"
@@ -555,6 +559,7 @@ int main(int argc, char **argv) {
   Req.VerboseVerbose = VerboseVerbose;
   Req.NoCanonicalizeWhiteSpace = NoCanonicalizeWhiteSpace;
   Req.MatchFullLines = MatchFullLines;
+  Req.IgnoreCase = IgnoreCase;
 
   if (VerboseVerbose)
     Req.Verbose = true;