Index: src/org/openstreetmap/josm/gui/preferences/display/LanguagePreference.java
===================================================================
--- src/org/openstreetmap/josm/gui/preferences/display/LanguagePreference.java	(revision 14915)
+++ src/org/openstreetmap/josm/gui/preferences/display/LanguagePreference.java	(working copy)
@@ -4,6 +4,7 @@
 import static org.openstreetmap.josm.tools.I18n.tr;
 
 import java.awt.Component;
+import java.text.Collator;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -83,7 +84,9 @@
 
         LanguageComboBoxModel() {
             data.add(0, null);
-            data.addAll(Arrays.asList(I18n.getAvailableTranslations()));
+            List<Locale> locales = Arrays.asList(I18n.getAvailableTranslations());
+            locales.sort((l1,l2) -> Collator.getInstance().compare(l1.getDisplayLanguage(), l2.getDisplayLanguage()));
+            data.addAll(locales);
         }
 
         private void selectLanguage(String language) {