diff --git a/icu4c/source/common/ucasemap.cpp b/icu4c/source/common/ucasemap.cpp
index 99e30c9..cc998c9 100644
--- a/icu4c/source/common/ucasemap.cpp
+++ b/icu4c/source/common/ucasemap.cpp
@@ -687,13 +687,13 @@
             if (change) {
                 ByteSinkUtil::appendTwoBytes(upper, sink);
                 if ((data & HAS_EITHER_DIALYTIKA) != 0) {
-                    sink.Append(u8"\u0308", 2);  // restore or add a dialytika
+                    sink.Append(reinterpret_cast<const char*>(u8"\u0308"), 2);  // restore or add a dialytika
                 }
                 if (addTonos) {
-                    sink.Append(u8"\u0301", 2);
+                    sink.Append(reinterpret_cast<const char*>(u8"\u0301"), 2);
                 }
                 while (numYpogegrammeni > 0) {
-                    sink.Append(u8"\u0399", 2);
+                    sink.Append(reinterpret_cast<const char*>(u8"\u0399"), 2);
                     --numYpogegrammeni;
                 }
             }
diff --git a/icu4c/source/test/intltest/collationtest.cpp b/icu4c/source/test/intltest/collationtest.cpp
index 4185494..9562e4d 100644
--- a/icu4c/source/test/intltest/collationtest.cpp
+++ b/icu4c/source/test/intltest/collationtest.cpp
@@ -295,13 +295,13 @@
 
     static const char *strings[] = {
         // string with U+FFFD == illegal byte sequence
-        u8"a\uFFFDz", "a\x80z",  // trail byte
-        u8"a\uFFFD\uFFFDz", "a\xc1\x81z",  // non-shortest form
-        u8"a\uFFFD\uFFFD\uFFFDz", "a\xe0\x82\x83z",  // non-shortest form
-        u8"a\uFFFD\uFFFD\uFFFDz", "a\xed\xa0\x80z",  // lead surrogate: would be U+D800
-        u8"a\uFFFD\uFFFD\uFFFDz", "a\xed\xbf\xbfz",  // trail surrogate: would be U+DFFF
-        u8"a\uFFFD\uFFFD\uFFFD\uFFFDz", "a\xf0\x8f\xbf\xbfz",  // non-shortest form
-        u8"a\uFFFD\uFFFD\uFFFD\uFFFDz", "a\xf4\x90\x80\x80z"  // out of range: would be U+110000
+        reinterpret_cast<const char*>(u8"a\uFFFDz"),                    reinterpret_cast<const char*>("a\x80z"),  // trail byte
+        reinterpret_cast<const char*>(u8"a\uFFFD\uFFFDz"),              reinterpret_cast<const char*>("a\xc1\x81z"),  // non-shortest form
+        reinterpret_cast<const char*>(u8"a\uFFFD\uFFFD\uFFFDz"),        reinterpret_cast<const char*>("a\xe0\x82\x83z"),  // non-shortest form
+        reinterpret_cast<const char*>(u8"a\uFFFD\uFFFD\uFFFDz"),        reinterpret_cast<const char*>("a\xed\xa0\x80z"),  // lead surrogate: would be U+D800
+        reinterpret_cast<const char*>(u8"a\uFFFD\uFFFD\uFFFDz"),        reinterpret_cast<const char*>("a\xed\xbf\xbfz"),  // trail surrogate: would be U+DFFF
+        reinterpret_cast<const char*>(u8"a\uFFFD\uFFFD\uFFFD\uFFFDz"),  reinterpret_cast<const char*>("a\xf0\x8f\xbf\xbfz"),  // non-shortest form
+        reinterpret_cast<const char*>(u8"a\uFFFD\uFFFD\uFFFD\uFFFDz"),  reinterpret_cast<const char*>("a\xf4\x90\x80\x80z")  // out of range: would be U+110000
     };
 
     for(int32_t i = 0; i < UPRV_LENGTHOF(strings); i += 2) {
diff --git a/icu4c/source/test/intltest/compactdecimalformattest.cpp b/icu4c/source/test/intltest/compactdecimalformattest.cpp
index 5f25ced..90afecd 100644
--- a/icu4c/source/test/intltest/compactdecimalformattest.cpp
+++ b/icu4c/source/test/intltest/compactdecimalformattest.cpp
@@ -185,38 +185,38 @@
         {123456789012345.0, "\\u00A5120\\u4E07\\u4EBF"},
 };
 static ExpectedResult kGermanCurrencyTestData[] = {
-        {1.0, u8"1\\u00A0\\u20AC"},
-        {12.0, u8"12\\u00A0\\u20AC"},
-        {123.0, u8"120\\u00A0\\u20AC"},
-        {1234.0, u8"1200\\u00A0\\u20AC"},
-        {12345.0, u8"12.000\\u00A0\\u20AC"},
-        {123456.0, u8"120.000\\u00A0\\u20AC"},
-        {1234567.0, u8"1,2\\u00A0Mio.\\u00A0\\u20AC"},
-        {12345678.0, u8"12\\u00A0Mio.\\u00A0\\u20AC"},
-        {123456789.0, u8"120\\u00A0Mio.\\u00A0\\u20AC"},
-        {1234567890.0, u8"1,2\\u00A0Mrd.\\u00A0\\u20AC"},
-        {12345678901.0, u8"12\\u00A0Mrd.\\u00A0\\u20AC"},
-        {123456789012.0, u8"120\\u00A0Mrd.\\u00A0\\u20AC"},
-        {1234567890123.0, u8"1,2\\u00A0Bio.\\u00A0\\u20AC"},
-        {12345678901234.0, u8"12\\u00A0Bio.\\u00A0\\u20AC"},
-        {123456789012345.0, u8"120\\u00A0Bio.\\u00A0\\u20AC"},
+        {1.0, reinterpret_cast<const char*>(u8"1\\u00A0\\u20AC")},
+        {12.0, reinterpret_cast<const char*>(u8"12\\u00A0\\u20AC")},
+        {123.0, reinterpret_cast<const char*>(u8"120\\u00A0\\u20AC")},
+        {1234.0, reinterpret_cast<const char*>(u8"1200\\u00A0\\u20AC")},
+        {12345.0, reinterpret_cast<const char*>(u8"12.000\\u00A0\\u20AC")},
+        {123456.0, reinterpret_cast<const char*>(u8"120.000\\u00A0\\u20AC")},
+        {1234567.0, reinterpret_cast<const char*>(u8"1,2\\u00A0Mio.\\u00A0\\u20AC")},
+        {12345678.0, reinterpret_cast<const char*>(u8"12\\u00A0Mio.\\u00A0\\u20AC")},
+        {123456789.0, reinterpret_cast<const char*>(u8"120\\u00A0Mio.\\u00A0\\u20AC")},
+        {1234567890.0, reinterpret_cast<const char*>(u8"1,2\\u00A0Mrd.\\u00A0\\u20AC")},
+        {12345678901.0, reinterpret_cast<const char*>(u8"12\\u00A0Mrd.\\u00A0\\u20AC")},
+        {123456789012.0, reinterpret_cast<const char*>(u8"120\\u00A0Mrd.\\u00A0\\u20AC")},
+        {1234567890123.0, reinterpret_cast<const char*>(u8"1,2\\u00A0Bio.\\u00A0\\u20AC")},
+        {12345678901234.0, reinterpret_cast<const char*>(u8"12\\u00A0Bio.\\u00A0\\u20AC")},
+        {123456789012345.0, reinterpret_cast<const char*>(u8"120\\u00A0Bio.\\u00A0\\u20AC")},
 };
 static ExpectedResult kEnglishCurrencyTestData[] = {
-        {1.0, u8"$1"},
-        {12.0, u8"$12"},
-        {123.0, u8"$120"},
-        {1234.0, u8"$1.2K"},
-        {12345.0, u8"$12K"},
-        {123456.0, u8"$120K"},
-        {1234567.0, u8"$1.2M"},
-        {12345678.0, u8"$12M"},
-        {123456789.0, u8"$120M"},
-        {1234567890.0, u8"$1.2B"},
-        {12345678901.0, u8"$12B"},
-        {123456789012.0, u8"$120B"},
-        {1234567890123.0, u8"$1.2T"},
-        {12345678901234.0, u8"$12T"},
-        {123456789012345.0, u8"$120T"},
+        {1.0, reinterpret_cast<const char*>(u8"$1")},
+        {12.0, reinterpret_cast<const char*>(u8"$12")},
+        {123.0, reinterpret_cast<const char*>(u8"$120")},
+        {1234.0, reinterpret_cast<const char*>(u8"$1.2K")},
+        {12345.0, reinterpret_cast<const char*>(u8"$12K")},
+        {123456.0, reinterpret_cast<const char*>(u8"$120K")},
+        {1234567.0, reinterpret_cast<const char*>(u8"$1.2M")},
+        {12345678.0, reinterpret_cast<const char*>(u8"$12M")},
+        {123456789.0, reinterpret_cast<const char*>(u8"$120M")},
+        {1234567890.0, reinterpret_cast<const char*>(u8"$1.2B")},
+        {12345678901.0, reinterpret_cast<const char*>(u8"$12B")},
+        {123456789012.0, reinterpret_cast<const char*>(u8"$120B")},
+        {1234567890123.0, reinterpret_cast<const char*>(u8"$1.2T")},
+        {12345678901234.0, reinterpret_cast<const char*>(u8"$12T")},
+        {123456789012345.0, reinterpret_cast<const char*>(u8"$120T")},
 };
 
 
diff --git a/icu4c/source/test/intltest/regextst.cpp b/icu4c/source/test/intltest/regextst.cpp
index 681ae11..efec8fd 100644
--- a/icu4c/source/test/intltest/regextst.cpp
+++ b/icu4c/source/test/intltest/regextst.cpp
@@ -5830,9 +5830,9 @@
     REGEX_ASSERT(status == U_REGEX_TIME_OUT);
 
     // UText, wrapping non-UTF-16 text, also takes a different execution path.
-    const char *text8 = u8"¿Qué es Unicode?  Unicode proporciona un número único para cada"
+    const char *text8 = reinterpret_cast<const char*>(u8"¿Qué es Unicode?  Unicode proporciona un número único para cada"
                           "carácter, sin importar la plataforma, sin importar el programa,"
-                          "sin importar el idioma.";
+                          "sin importar el idioma.");
     status = U_ZERO_ERROR;
     LocalUTextPointer ut(utext_openUTF8(NULL, text8, -1, &status));
     REGEX_CHECK_STATUS;
diff --git a/icu4c/source/test/intltest/strcase.cpp b/icu4c/source/test/intltest/strcase.cpp
index 9b753e4..dc81fb4 100644
--- a/icu4c/source/test/intltest/strcase.cpp
+++ b/icu4c/source/test/intltest/strcase.cpp
@@ -1314,7 +1314,7 @@
     Edits edits;
 
     int32_t length = CaseMap::utf8ToLower("tr", U_OMIT_UNCHANGED_TEXT,
-                                          u8"IstanBul", 8, dest, UPRV_LENGTHOF(dest), &edits, errorCode);
+                                          reinterpret_cast<const char*>(u8"IstanBul"), 8, dest, UPRV_LENGTHOF(dest), &edits, errorCode);
     assertEquals(u"toLower(IstanBul)", UnicodeString(u"ıb"),
                  UnicodeString::fromUTF8(StringPiece(dest, length)));
     static const EditChange lowerExpectedChanges[] = {
@@ -1330,7 +1330,7 @@
 
     edits.reset();
     length = CaseMap::utf8ToUpper("el", U_OMIT_UNCHANGED_TEXT,
-                                  u8"Πατάτα", 6 * 2, dest, UPRV_LENGTHOF(dest), &edits, errorCode);
+                                  reinterpret_cast<const char*>(u8"Πατάτα"), 6 * 2, dest, UPRV_LENGTHOF(dest), &edits, errorCode);
     assertEquals(u"toUpper(Πατάτα)", UnicodeString(u"ΑΤΑΤΑ"),
                  UnicodeString::fromUTF8(StringPiece(dest, length)));
     static const EditChange upperExpectedChanges[] = {
@@ -1352,7 +1352,7 @@
                                   U_OMIT_UNCHANGED_TEXT |
                                   U_TITLECASE_NO_BREAK_ADJUSTMENT |
                                   U_TITLECASE_NO_LOWERCASE,
-                                  nullptr, u8"IjssEL IglOo", 12,
+                                  nullptr, reinterpret_cast<const char*>(u8"IjssEL IglOo"), 12,
                                   dest, UPRV_LENGTHOF(dest), &edits, errorCode);
     assertEquals(u"toTitle(IjssEL IglOo)", UnicodeString(u"J"),
                  UnicodeString::fromUTF8(StringPiece(dest, length)));
@@ -1370,7 +1370,7 @@
     // No explicit nor automatic edits.reset(). Edits should be appended.
     length = CaseMap::utf8Fold(U_OMIT_UNCHANGED_TEXT | U_EDITS_NO_RESET |
                                    U_FOLD_CASE_EXCLUDE_SPECIAL_I,
-                               u8"IßtanBul", 1 + 2 + 6, dest, UPRV_LENGTHOF(dest), &edits, errorCode);
+                               reinterpret_cast<const char*>(u8"IßtanBul"), 1 + 2 + 6, dest, UPRV_LENGTHOF(dest), &edits, errorCode);
     assertEquals(u"foldCase(IßtanBul)", UnicodeString(u"ıssb"),
                  UnicodeString::fromUTF8(StringPiece(dest, length)));
     static const EditChange foldExpectedChanges[] = {
@@ -1454,44 +1454,44 @@
     StringByteSink<std::string> sink(&dest);
 
     // Omit unchanged text.
-    CaseMap::utf8ToLower("tr", U_OMIT_UNCHANGED_TEXT, u8"IstanBul", sink, nullptr, errorCode);
+    CaseMap::utf8ToLower("tr", U_OMIT_UNCHANGED_TEXT, reinterpret_cast<const char*>(u8"IstanBul"), sink, nullptr, errorCode);
     assertEquals(u"toLower(IstanBul)", UnicodeString(u"ıb"), UnicodeString::fromUTF8(dest));
     dest.clear();
-    CaseMap::utf8ToUpper("el", U_OMIT_UNCHANGED_TEXT, u8"Πατάτα", sink, nullptr, errorCode);
+    CaseMap::utf8ToUpper("el", U_OMIT_UNCHANGED_TEXT, reinterpret_cast<const char*>(u8"Πατάτα"), sink, nullptr, errorCode);
     assertEquals(u"toUpper(Πατάτα)", UnicodeString(u"ΑΤΑΤΑ"),
                  UnicodeString::fromUTF8(dest));
 #if !UCONFIG_NO_BREAK_ITERATION
     dest.clear();
     CaseMap::utf8ToTitle(
         "nl", U_OMIT_UNCHANGED_TEXT | U_TITLECASE_NO_BREAK_ADJUSTMENT | U_TITLECASE_NO_LOWERCASE,
-        nullptr, u8"IjssEL IglOo", sink, nullptr, errorCode);
+        nullptr, reinterpret_cast<const char*>(u8"IjssEL IglOo"), sink, nullptr, errorCode);
     assertEquals(u"toTitle(IjssEL IglOo)", UnicodeString(u"J"),
                  UnicodeString::fromUTF8(dest));
 #endif
     dest.clear();
     CaseMap::utf8Fold(U_OMIT_UNCHANGED_TEXT | U_FOLD_CASE_EXCLUDE_SPECIAL_I,
-                      u8"IßtanBul", sink, nullptr, errorCode);
+                      reinterpret_cast<const char*>(u8"IßtanBul"), sink, nullptr, errorCode);
     assertEquals(u"foldCase(IßtanBul)", UnicodeString(u"ıssb"),
                  UnicodeString::fromUTF8(dest));
 
     // Return the whole result string.
     dest.clear();
-    CaseMap::utf8ToLower("tr", 0, u8"IstanBul", sink, nullptr, errorCode);
+    CaseMap::utf8ToLower("tr", 0, reinterpret_cast<const char*>(u8"IstanBul"), sink, nullptr, errorCode);
     assertEquals(u"toLower(IstanBul)", UnicodeString(u"ıstanbul"),
                  UnicodeString::fromUTF8(dest));
     dest.clear();
-    CaseMap::utf8ToUpper("el", 0, u8"Πατάτα", sink, nullptr, errorCode);
+    CaseMap::utf8ToUpper("el", 0, reinterpret_cast<const char*>(u8"Πατάτα"), sink, nullptr, errorCode);
     assertEquals(u"toUpper(Πατάτα)", UnicodeString(u"ΠΑΤΑΤΑ"),
                  UnicodeString::fromUTF8(dest));
 #if !UCONFIG_NO_BREAK_ITERATION
     dest.clear();
     CaseMap::utf8ToTitle("nl", U_TITLECASE_NO_BREAK_ADJUSTMENT | U_TITLECASE_NO_LOWERCASE,
-                         nullptr, u8"IjssEL IglOo", sink, nullptr, errorCode);
+                         nullptr, reinterpret_cast<const char*>(u8"IjssEL IglOo"), sink, nullptr, errorCode);
     assertEquals(u"toTitle(IjssEL IglOo)", UnicodeString(u"IJssEL IglOo"),
                  UnicodeString::fromUTF8(dest));
 #endif
     dest.clear();
-    CaseMap::utf8Fold(U_FOLD_CASE_EXCLUDE_SPECIAL_I, u8"IßtanBul", sink, nullptr, errorCode);
+    CaseMap::utf8Fold(U_FOLD_CASE_EXCLUDE_SPECIAL_I, reinterpret_cast<const char*>(u8"IßtanBul"), sink, nullptr, errorCode);
     assertEquals(u"foldCase(IßtanBul)", UnicodeString(u"ısstanbul"),
                  UnicodeString::fromUTF8(dest));
 }
diff --git a/icu4c/source/test/intltest/tstnorm.cpp b/icu4c/source/test/intltest/tstnorm.cpp
index b3f4185..886df6f 100644
--- a/icu4c/source/test/intltest/tstnorm.cpp
+++ b/icu4c/source/test/intltest/tstnorm.cpp
@@ -1574,8 +1574,8 @@
         return;
     }
     static const char *const src =
-        u8"  AÄA\u0308A\u0308\u00ad\u0323Ä\u0323,\u00ad\u1100\u1161가\u11A8가\u3133  ";
-    std::string expected = u8"  aääạ\u0308ạ\u0308,가각갃  ";
+        reinterpret_cast<const char*>(u8"  AÄA\u0308A\u0308\u00ad\u0323Ä\u0323,\u00ad\u1100\u1161가\u11A8가\u3133  ");
+    std::string expected = reinterpret_cast<const char*>(u8"  aääạ\u0308ạ\u0308,가각갃  ");
     std::string result;
     StringByteSink<std::string> sink(&result, static_cast<int32_t>(expected.length()));
     Edits edits;
@@ -1607,7 +1607,7 @@
     assertTrue("isNormalizedUTF8(normalized)", nfkc_cf->isNormalizedUTF8(result, errorCode));
 
     // Omit unchanged text.
-    expected = u8"aääạ\u0308ạ\u0308가각갃";
+    expected = reinterpret_cast<const char*>(u8"aääạ\u0308ạ\u0308가각갃");
     result.clear();
     edits.reset();
     nfkc_cf->normalizeUTF8(U_OMIT_UNCHANGED_TEXT, src, sink, &edits, errorCode);
@@ -1623,7 +1623,7 @@
     // With filter: The normalization code does not see the "A" substrings.
     UnicodeSet filter(u"[^A]", errorCode);
     FilteredNormalizer2 fn2(*nfkc_cf, filter);
-    expected = u8"  AäA\u0308A\u0323\u0308ạ\u0308,가각갃  ";
+    expected = reinterpret_cast<const char*>(u8"  AäA\u0308A\u0323\u0308ạ\u0308,가각갃  ");
     result.clear();
     edits.reset();
     fn2.normalizeUTF8(0, src, sink, &edits, errorCode);
@@ -1655,7 +1655,7 @@
     // Omit unchanged text.
     // Note that the result is not normalized because the inner normalizer
     // does not see text across filter spans.
-    expected = u8"ä\u0323\u0308ạ\u0308가각갃";
+    expected = reinterpret_cast<const char*>(u8"ä\u0323\u0308ạ\u0308가각갃");
     result.clear();
     edits.reset();
     fn2.normalizeUTF8(U_OMIT_UNCHANGED_TEXT, src, sink, &edits, errorCode);
@@ -1743,16 +1743,16 @@
     assertSuccess("normalize", errorCode.get());
     assertEquals("normalize", expected, result);
 
-    std::string src8(u8"  A");
-    src8.append("\x80").append(u8"ÄA\u0308").append("\xC0\x80").
-        append(u8"A\u0308\u00ad\u0323").append("\xED\xA0\x80").
-        append(u8"Ä\u0323,\u00ad").append("\xF4\x90\x80\x80").
-        append(u8"\u1100\u1161가\u11A8가\u3133  ").append("\xF0");
-    std::string expected8(u8"  a");
-    expected8.append("\x80").append(u8"ää").append("\xC0\x80").
-        append(u8"ạ\u0308").append("\xED\xA0\x80").
-        append(u8"ạ\u0308,").append("\xF4\x90\x80\x80").
-        append(u8"가각갃  ").append("\xF0");
+    std::string src8(reinterpret_cast<const char*>(u8"  A"));
+    src8.append("\x80").append(reinterpret_cast<const char*>(u8"ÄA\u0308")).append("\xC0\x80").
+        append(reinterpret_cast<const char*>(u8"A\u0308\u00ad\u0323")).append("\xED\xA0\x80").
+        append(reinterpret_cast<const char*>(u8"Ä\u0323,\u00ad")).append("\xF4\x90\x80\x80").
+        append(reinterpret_cast<const char*>(u8"\u1100\u1161가\u11A8가\u3133  ")).append("\xF0");
+    std::string expected8(reinterpret_cast<const char*>(u8"  a"));
+    expected8.append("\x80").append(reinterpret_cast<const char*>(u8"ää")).append("\xC0\x80").
+        append(reinterpret_cast<const char*>(u8"ạ\u0308")).append("\xED\xA0\x80").
+        append(reinterpret_cast<const char*>(u8"ạ\u0308,")).append("\xF4\x90\x80\x80").
+        append(reinterpret_cast<const char*>(u8"가각갃  ")).append("\xF0");
     std::string result8;
     StringByteSink<std::string> sink(&result8);
     nfkc_cf->normalizeUTF8(0, src8, sink, nullptr, errorCode);
@@ -1777,8 +1777,8 @@
     assertFalse("isNormalized(LV+11A7)", nfkc->isNormalized(s, errorCode));
     assertTrue("isNormalized(normalized)", nfkc->isNormalized(result, errorCode));
 
-    std::string s8(u8"\u1100\u1161\u11A7\u1100\u314F\u11A7가\u11A7");
-    std::string expected8(u8"가\u11A7가\u11A7가\u11A7");
+    std::string s8(reinterpret_cast<const char*>(u8"\u1100\u1161\u11A7\u1100\u314F\u11A7가\u11A7"));
+    std::string expected8(reinterpret_cast<const char*>(u8"가\u11A7가\u11A7가\u11A7"));
     std::string result8;
     StringByteSink<std::string> sink(&result8, static_cast<int32_t>(expected8.length()));
     nfkc->normalizeUTF8(0, s8, sink, nullptr, errorCode);
diff --git a/icu4c/source/test/intltest/uts46test.cpp b/icu4c/source/test/intltest/uts46test.cpp
index 1a9bd6b..e11fdf2 100644
--- a/icu4c/source/test/intltest/uts46test.cpp
+++ b/icu4c/source/test/intltest/uts46test.cpp
@@ -935,7 +935,7 @@
         if (*status != u'[') {
             errln("%s  status field does not start with '[': %s\n    %s", type, status, line);
         }
-        if (strcmp(status, u8"[]") != 0) {
+        if (strcmp(status, reinterpret_cast<const char*>(u8"[]")) != 0) {
             expectedHasErrors = TRUE;
         }
     }