diff --git a/icu4c/source/common/loclikelysubtags.cpp b/icu4c/source/common/loclikelysubtags.cpp
index 8800111d166e..3eed4361b337 100644
--- a/icu4c/source/common/loclikelysubtags.cpp
+++ b/icu4c/source/common/loclikelysubtags.cpp
@@ -709,7 +709,7 @@ LSR LikelySubtags::maximize(StringPiece language, StringPiece script, StringPiec
                 matchRegion = true;
             }
         } else {
-            retainRegion = true;
+            retainRegion = !region.empty() && !isMacroregion(region, errorCode);
             if (state == 0) {
                 value = defaultLsrIndex;
             } else {
diff --git a/icu4c/source/test/intltest/loctest.cpp b/icu4c/source/test/intltest/loctest.cpp
index 8134fca6ae15..1a4b9869679e 100644
--- a/icu4c/source/test/intltest/loctest.cpp
+++ b/icu4c/source/test/intltest/loctest.cpp
@@ -3832,8 +3832,8 @@ LocaleTest::TestAddLikelyAndMinimizeSubtags() {
             "es_419"
         }, {
             "und_150",
-            "en_Latn_150",
-            "en_150"
+            "en_Latn_US",
+            "en"
         }, {
             "und_AT",
             "de_Latn_AT",
diff --git a/icu4c/source/test/testdata/cldr/localeIdentifiers/likelySubtags.txt b/icu4c/source/test/testdata/cldr/localeIdentifiers/likelySubtags.txt
index 1f9e3557fff3..a7bd27364f74 100644
--- a/icu4c/source/test/testdata/cldr/localeIdentifiers/likelySubtags.txt
+++ b/icu4c/source/test/testdata/cldr/localeIdentifiers/likelySubtags.txt
@@ -980,8 +980,8 @@ uk-Cyrl ;	uk-Cyrl-UA ;	uk ;
 uk-Egyp ;	uk-Egyp-UA ;	uk-Egyp ;	
 uk-UA ;	uk-Cyrl-UA ;	uk ;	
 und ;	en-Latn-US ;	en ;	
-und-001 ;	en-Latn-001 ;	en-001 ;	
-und-150 ;	en-Latn-150 ;	en-150 ;	
+und-001 ;	en-Latn-US ;	en ;	
+und-150 ;	en-Latn-US ;	en ;	
 und-419 ;	es-Latn-419 ;	es-419 ;	
 und-AD ;	ca-Latn-AD ;	ca-AD ;	
 und-AE ;	ar-Arab-AE ;	ar-AE ;	
@@ -1014,7 +1014,7 @@ und-Adlm-NG ;	ff-Adlm-NG ;	 ;
 und-Adlm-SL ;	ff-Adlm-SL ;	 ;	
 und-Adlm-SN ;	ff-Adlm-SN ;	 ;	
 und-Arab ;	ar-Arab-EG ;	ar ;	
-und-Arab-001 ;	ar-Arab-001 ;	ar-001 ;	
+und-Arab-001 ;	ar-Arab-EG ;	ar ;	
 und-Arab-AE ;	ar-Arab-AE ;	ar-AE ;	
 und-Arab-AF ;	fa-Arab-AF ;	fa-AF ;	
 und-Arab-AQ ;	ar-Arab-AQ ;	ar-AQ ;	
@@ -1255,8 +1255,8 @@ und-Laoo ;	lo-Laoo-LA ;	lo ;
 und-Laoo-AQ ;	lo-Laoo-AQ ;	lo-AQ ;	
 und-Laoo-LA ;	lo-Laoo-LA ;	lo ;	
 und-Latn ;	en-Latn-US ;	en ;	
-und-Latn-001 ;	en-Latn-001 ;	en-001 ;	
-und-Latn-150 ;	en-Latn-150 ;	en-150 ;	
+und-Latn-001 ;	en-Latn-US ;	en ;	
+und-Latn-150 ;	en-Latn-US ;	en ;	
 und-Latn-419 ;	es-Latn-419 ;	es-419 ;	
 und-Latn-AD ;	ca-Latn-AD ;	ca-AD ;	
 und-Latn-AE ;	en-Latn-AE ;	en-AE ;	
diff --git a/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/util/ULocaleTest.java b/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/util/ULocaleTest.java
index 4c6e36cc00a4..4e89791c4b47 100644
--- a/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/util/ULocaleTest.java
+++ b/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/util/ULocaleTest.java
@@ -4114,8 +4114,8 @@ else if (!res.toString().equals(exp)) {
                     "es_419"
                 }, {
                     "und_150",
-                    "en_Latn_150",
-                    "en_150"
+                    "en_Latn_US",
+                    "en"
                 }, {
                     "und_AT",
                     "de_Latn_AT",
diff --git a/icu4j/main/core/src/main/java/com/ibm/icu/impl/locale/LikelySubtags.java b/icu4j/main/core/src/main/java/com/ibm/icu/impl/locale/LikelySubtags.java
index 6d5a35379378..bcee84660b0f 100644
--- a/icu4j/main/core/src/main/java/com/ibm/icu/impl/locale/LikelySubtags.java
+++ b/icu4j/main/core/src/main/java/com/ibm/icu/impl/locale/LikelySubtags.java
@@ -269,7 +269,12 @@ private LSR makeMaximizedLsr(String language, String script, String region, Stri
      * Helper method to find out a region is a macroregion
      */
     private boolean isMacroregion(String region) {
-        Region.RegionType type = Region.getInstance(region).getType();
+        Region.RegionType type;
+        try {
+            type = Region.getInstance(region).getType();
+        } catch (Exception e) {
+            return false;  // return false for unrecognized region.
+        }
         return type == Region.RegionType.WORLD ||
             type == Region.RegionType.CONTINENT ||
             type == Region.RegionType.SUBCONTINENT ;
@@ -356,7 +361,7 @@ private LSR maximize(String language, String script, String region, boolean retu
                     matchRegion = true;
                 }
             } else {
-                retainRegion = true;
+                retainRegion = !region.isEmpty() && !isMacroregion(region);
                 if (state == 0) {
                     value = defaultLsrIndex;
                 } else {
diff --git a/icu4j/main/core/src/test/resources/com/ibm/icu/dev/data/cldr/localeIdentifiers/likelySubtags.txt b/icu4j/main/core/src/test/resources/com/ibm/icu/dev/data/cldr/localeIdentifiers/likelySubtags.txt
index 1f9e3557fff3..a7bd27364f74 100644
--- a/icu4j/main/core/src/test/resources/com/ibm/icu/dev/data/cldr/localeIdentifiers/likelySubtags.txt
+++ b/icu4j/main/core/src/test/resources/com/ibm/icu/dev/data/cldr/localeIdentifiers/likelySubtags.txt
@@ -980,8 +980,8 @@ uk-Cyrl ;	uk-Cyrl-UA ;	uk ;
 uk-Egyp ;	uk-Egyp-UA ;	uk-Egyp ;	
 uk-UA ;	uk-Cyrl-UA ;	uk ;	
 und ;	en-Latn-US ;	en ;	
-und-001 ;	en-Latn-001 ;	en-001 ;	
-und-150 ;	en-Latn-150 ;	en-150 ;	
+und-001 ;	en-Latn-US ;	en ;	
+und-150 ;	en-Latn-US ;	en ;	
 und-419 ;	es-Latn-419 ;	es-419 ;	
 und-AD ;	ca-Latn-AD ;	ca-AD ;	
 und-AE ;	ar-Arab-AE ;	ar-AE ;	
@@ -1014,7 +1014,7 @@ und-Adlm-NG ;	ff-Adlm-NG ;	 ;
 und-Adlm-SL ;	ff-Adlm-SL ;	 ;	
 und-Adlm-SN ;	ff-Adlm-SN ;	 ;	
 und-Arab ;	ar-Arab-EG ;	ar ;	
-und-Arab-001 ;	ar-Arab-001 ;	ar-001 ;	
+und-Arab-001 ;	ar-Arab-EG ;	ar ;	
 und-Arab-AE ;	ar-Arab-AE ;	ar-AE ;	
 und-Arab-AF ;	fa-Arab-AF ;	fa-AF ;	
 und-Arab-AQ ;	ar-Arab-AQ ;	ar-AQ ;	
@@ -1255,8 +1255,8 @@ und-Laoo ;	lo-Laoo-LA ;	lo ;
 und-Laoo-AQ ;	lo-Laoo-AQ ;	lo-AQ ;	
 und-Laoo-LA ;	lo-Laoo-LA ;	lo ;	
 und-Latn ;	en-Latn-US ;	en ;	
-und-Latn-001 ;	en-Latn-001 ;	en-001 ;	
-und-Latn-150 ;	en-Latn-150 ;	en-150 ;	
+und-Latn-001 ;	en-Latn-US ;	en ;	
+und-Latn-150 ;	en-Latn-US ;	en ;	
 und-Latn-419 ;	es-Latn-419 ;	es-419 ;	
 und-Latn-AD ;	ca-Latn-AD ;	ca-AD ;	
 und-Latn-AE ;	en-Latn-AE ;	en-AE ;