diff --git a/clang/docs/ClangFormatStyleOptions.rst b/clang/docs/ClangFormatStyleOptions.rst
--- a/clang/docs/ClangFormatStyleOptions.rst
+++ b/clang/docs/ClangFormatStyleOptions.rst
@@ -2036,6 +2036,33 @@
   ``ClassImpl.hpp`` would not have the main include file put on top
   before any other include.
 
+**IncludeSortCaseAware** (``bool``)
+  Specify if sorting should be done in a case aware fashion.
+
+  By default, clang-format sorts includes in an ASCIIbetical
+  fashion. For instance:
+
+  .. code-block:: c++
+
+     #include "B/a.h"               into      #include "A/B.h"
+     #include "B/A.h"                         #include "A/b.h"
+     #include "A/B.h"                         #include "B/A.h"
+     #include "a/b.h"                         #include "B/a.h"
+     #include "A/b.h"                         #include "a/b.h"
+
+  This option will cause includes to be sorted alphabetically with case
+  used as a tie-breaker. For instance:
+
+  .. code-block:: c++
+
+     #include "B/a.h"               into      #include "A/B.h"
+     #include "B/A.h"                         #include "A/b.h"
+     #include "A/B.h"                         #include "a/b.h"
+     #include "a/b.h"                         #include "B/A.h"
+     #include "A/b.h"                         #include "B/a.h"
+
+  This option is off by default.
+
 **IndentCaseBlocks** (``bool``)
   Indent case label blocks one level from the case label.
 
diff --git a/clang/include/clang/Tooling/Inclusions/IncludeStyle.h b/clang/include/clang/Tooling/Inclusions/IncludeStyle.h
--- a/clang/include/clang/Tooling/Inclusions/IncludeStyle.h
+++ b/clang/include/clang/Tooling/Inclusions/IncludeStyle.h
@@ -147,6 +147,33 @@
   /// ``ClassImpl.hpp`` would not have the main include file put on top
   /// before any other include.
   std::string IncludeIsMainSourceRegex;
+
+  /// Specify if sorting should be done in a case aware fashion.
+  ///
+  /// By default, clang-format sorts includes in an ASCIIbetical
+  /// fashion. For instance:
+  ///
+  /// \code
+  ///    #include "B/a.h"               into      #include "A/B.h"
+  ///    #include "B/A.h"                         #include "A/b.h"
+  ///    #include "A/B.h"                         #include "B/A.h"
+  ///    #include "a/b.h"                         #include "B/a.h"
+  ///    #include "A/b.h"                         #include "a/b.h"
+  /// \endcode
+  ///
+  /// This option will cause includes to be sorted alphabetically with case
+  /// used as a tie-breaker. For instance:
+  ///
+  /// \code
+  ///    #include "B/a.h"               into      #include "A/B.h"
+  ///    #include "B/A.h"                         #include "A/b.h"
+  ///    #include "A/B.h"                         #include "a/b.h"
+  ///    #include "a/b.h"                         #include "B/A.h"
+  ///    #include "A/b.h"                         #include "B/a.h"
+  /// \endcode
+  ///
+  /// This option is off by default.
+  bool IncludeSortCaseAware;
 };
 
 } // namespace tooling
diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -556,6 +556,8 @@
     IO.mapOptional("IncludeIsMainRegex", Style.IncludeStyle.IncludeIsMainRegex);
     IO.mapOptional("IncludeIsMainSourceRegex",
                    Style.IncludeStyle.IncludeIsMainSourceRegex);
+    IO.mapOptional("IncludeSortCaseAware",
+                   Style.IncludeStyle.IncludeSortCaseAware);
     IO.mapOptional("IndentCaseLabels", Style.IndentCaseLabels);
     IO.mapOptional("IndentCaseBlocks", Style.IndentCaseBlocks);
     IO.mapOptional("IndentGotoLabels", Style.IndentGotoLabels);
@@ -2180,6 +2182,14 @@
     Indices.push_back(i);
   }
   llvm::stable_sort(Indices, [&](unsigned LHSI, unsigned RHSI) {
+    if (Style.IncludeStyle.IncludeSortCaseAware) {
+      const auto LHSFilenameLower = Includes[LHSI].Filename.lower();
+      const auto RHSFilenameLower = Includes[RHSI].Filename.lower();
+      return std::tie(Includes[LHSI].Priority, LHSFilenameLower,
+                      Includes[LHSI].Filename) <
+             std::tie(Includes[RHSI].Priority, RHSFilenameLower,
+                      Includes[RHSI].Filename);
+    }
     return std::tie(Includes[LHSI].Priority, Includes[LHSI].Filename) <
            std::tie(Includes[RHSI].Priority, Includes[RHSI].Filename);
   });
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -14395,6 +14395,8 @@
   CHECK_PARSE_BOOL(DeriveLineEnding);
   CHECK_PARSE_BOOL(DerivePointerAlignment);
   CHECK_PARSE_BOOL_FIELD(DerivePointerAlignment, "DerivePointerBinding");
+  CHECK_PARSE_BOOL_FIELD(IncludeStyle.IncludeSortCaseAware,
+                         "IncludeSortCaseAware");
   CHECK_PARSE_BOOL(DisableFormat);
   CHECK_PARSE_BOOL(IndentCaseLabels);
   CHECK_PARSE_BOOL(IndentCaseBlocks);
diff --git a/clang/unittests/Format/SortIncludesTest.cpp b/clang/unittests/Format/SortIncludesTest.cpp
--- a/clang/unittests/Format/SortIncludesTest.cpp
+++ b/clang/unittests/Format/SortIncludesTest.cpp
@@ -598,6 +598,47 @@
                  "a.cc"));
 }
 
+TEST_F(SortIncludesTest, SupportOptionalCaseAwareSorting) {
+  Style.IncludeSortCaseAware = true;
+
+  EXPECT_EQ("#include \"A/B.h\"\n"
+            "#include \"A/b.h\"\n"
+            "#include \"a/b.h\"\n"
+            "#include \"B/A.h\"\n"
+            "#include \"B/a.h\"\n",
+            sort("#include \"B/a.h\"\n"
+                 "#include \"B/A.h\"\n"
+                 "#include \"A/B.h\"\n"
+                 "#include \"a/b.h\"\n"
+                 "#include \"A/b.h\"\n",
+                 "a.h"));
+
+  Style.IncludeBlocks = clang::tooling::IncludeStyle::IBS_Regroup;
+  Style.IncludeCategories = {
+      {"^\"", 1, 0, false}, {"^<.*\\.h>$", 2, 0, false}, {"^<", 3, 0, false}};
+
+  StringRef UnsortedCode = "#include \"qt.h\"\n"
+                           "#include <algorithm>\n"
+                           "#include <qtwhatever.h>\n"
+                           "#include <Qtwhatever.h>\n"
+                           "#include <Algorithm>\n"
+                           "#include \"vlib.h\"\n"
+                           "#include \"Vlib.h\"\n"
+                           "#include \"AST.h\"\n";
+
+  EXPECT_EQ("#include \"AST.h\"\n"
+            "#include \"qt.h\"\n"
+            "#include \"Vlib.h\"\n"
+            "#include \"vlib.h\"\n"
+            "\n"
+            "#include <Qtwhatever.h>\n"
+            "#include <qtwhatever.h>\n"
+            "\n"
+            "#include <Algorithm>\n"
+            "#include <algorithm>\n",
+            sort(UnsortedCode));
+}
+
 TEST_F(SortIncludesTest, SupportCaseInsensitiveMatching) {
   // Setup an regex for main includes so we can cover those as well.
   Style.IncludeIsMainRegex = "([-_](test|unittest))?$";