diff --git a/src/corelib/time/qtimezoneprivate.cpp b/src/corelib/time/qtimezoneprivate.cpp
index ffbed73bf0..876f5ac371 100644
--- a/src/corelib/time/qtimezoneprivate.cpp
+++ b/src/corelib/time/qtimezoneprivate.cpp
@@ -626,7 +626,7 @@ static QList<QByteArray> selectAvailable(QList<QByteArrayView> &&desired,
     return result;
 }
 
-QList<QByteArray> QTimeZonePrivate::availableTimeZoneIds(QLocale::Territory territory) const
+QList<QByteArrayView> QTimeZonePrivate::matchingTimeZoneIds(QLocale::Territory territory) const
 {
     // Default fall-back mode, use the zoneTable to find Region of know Zones
     QList<QByteArrayView> regions;
@@ -644,10 +644,15 @@ QList<QByteArray> QTimeZonePrivate::availableTimeZoneIds(QLocale::Territory terr
             }
         }
     }
-    return selectAvailable(std::move(regions), availableTimeZoneIds());
+    return regions;
 }
 
-QList<QByteArray> QTimeZonePrivate::availableTimeZoneIds(int offsetFromUtc) const
+QList<QByteArray> QTimeZonePrivate::availableTimeZoneIds(QLocale::Territory territory) const
+{
+    return selectAvailable(matchingTimeZoneIds(territory), availableTimeZoneIds());
+}
+
+QList<QByteArrayView> QTimeZonePrivate::matchingTimeZoneIds(int offsetFromUtc) const
 {
     // Default fall-back mode: use the zoneTable to find offsets of know zones.
     QList<QByteArrayView> offsets;
@@ -662,7 +667,12 @@ QList<QByteArray> QTimeZonePrivate::availableTimeZoneIds(int offsetFromUtc) cons
             }
         }
     }
-    return selectAvailable(std::move(offsets), availableTimeZoneIds());
+    return offsets;
+}
+
+QList<QByteArray> QTimeZonePrivate::availableTimeZoneIds(int offsetFromUtc) const
+{
+    return selectAvailable(matchingTimeZoneIds(offsetFromUtc), availableTimeZoneIds());
 }
 
 #ifndef QT_NO_DATASTREAM
diff --git a/src/corelib/time/qtimezoneprivate_icu.cpp b/src/corelib/time/qtimezoneprivate_icu.cpp
index 8369a42f22..c7039e157c 100644
--- a/src/corelib/time/qtimezoneprivate_icu.cpp
+++ b/src/corelib/time/qtimezoneprivate_icu.cpp
@@ -425,6 +425,8 @@ QList<QByteArray> QIcuTimeZonePrivate::availableTimeZoneIds(QLocale::Territory t
     if (U_SUCCESS(status))
         result = uenumToIdList(uenum);
     uenum_close(uenum);
+    // We could merge in what matchingTimeZoneIds(territory) gives us, but
+    // hopefully that's redundant, as ICU packages CLDR.
     return result;
 }
 
@@ -439,6 +441,8 @@ QList<QByteArray> QIcuTimeZonePrivate::availableTimeZoneIds(int offsetFromUtc) c
     if (U_SUCCESS(status))
         result = uenumToIdList(uenum);
     uenum_close(uenum);
+    // We could merge in what matchingTimeZoneIds(offsetFromUtc) gives us, but
+    // hopefully that's redundant, as ICU packages CLDR.
     return result;
 #else
     return QTimeZonePrivate::availableTimeZoneIds(offsetFromUtc);
diff --git a/src/corelib/time/qtimezoneprivate_p.h b/src/corelib/time/qtimezoneprivate_p.h
index fcaab52db4..d54220b6e6 100644
--- a/src/corelib/time/qtimezoneprivate_p.h
+++ b/src/corelib/time/qtimezoneprivate_p.h
@@ -153,6 +153,12 @@ public:
         return QByteArrayLiteral("UTC");
     }
 
+protected:
+    // Zones CLDR data says match a condition.
+    // Use to filter what the backend has available.
+    QList<QByteArrayView> matchingTimeZoneIds(QLocale::Territory territory) const;
+    QList<QByteArrayView> matchingTimeZoneIds(int utcOffset) const;
+
 #if QT_CONFIG(timezone_locale)
 private:
     // Defined in qtimezonelocale.cpp
diff --git a/src/corelib/time/qtimezoneprivate_tz.cpp b/src/corelib/time/qtimezoneprivate_tz.cpp
index c31b4dc965..253f1367d9 100644
--- a/src/corelib/time/qtimezoneprivate_tz.cpp
+++ b/src/corelib/time/qtimezoneprivate_tz.cpp
@@ -41,6 +41,7 @@ using namespace Qt::StringLiterals;
 */
 
 struct QTzTimeZone {
+    // TODO: for zone1970.tab we'll need a set of territories:
     QLocale::Territory territory = QLocale::AnyTerritory;
     QByteArray comment;
 };
@@ -80,7 +81,7 @@ static bool openZoneInfo(const QString &name, QFile *file)
 
 // Parse zone.tab table for territory information, read directories to ensure we
 // find all installed zones (many are omitted from zone.tab; even more from
-// zone1970.tab).
+// zone1970.tab; see also QTBUG-64941).
 static QTzTimeZoneHash loadTzTimeZones()
 {
     QFile tzif;
@@ -1250,13 +1251,38 @@ QList<QByteArray> QTzTimeZonePrivate::availableTimeZoneIds() const
 
 QList<QByteArray> QTzTimeZonePrivate::availableTimeZoneIds(QLocale::Territory territory) const
 {
-    // TODO AnyTerritory
     QList<QByteArray> result;
     for (auto it = tzZones->cbegin(), end = tzZones->cend(); it != end; ++it) {
         if (it.value().territory == territory)
             result << it.key();
     }
     std::sort(result.begin(), result.end());
+
+    // Since zone.tab only knows about one territory per zone, and is somewhat
+    // incomplete, we may well miss some zones that CLDR associates with the
+    // territory. So merge with those from CLDR that we do support.
+    const auto unWantedZone = [territory](QByteArrayView id) {
+        // We only want to add zones if they are known and we don't already have them:
+        auto it = tzZones->constFind(id);
+        return it == tzZones->end() || it->territory == territory;
+    };
+    QList<QByteArrayView> cldrViews = matchingTimeZoneIds(territory);
+    std::sort(cldrViews.begin(), cldrViews.end());
+    const auto uniqueEnd = std::unique(cldrViews.begin(), cldrViews.end());
+    const auto prunedEnd = std::remove_if(cldrViews.begin(), uniqueEnd, unWantedZone);
+    const auto cldrSize = std::distance(cldrViews.begin(), prunedEnd);
+    if (cldrSize) {
+        QList<QByteArray> cldrList;
+        cldrList.reserve(cldrSize);
+        for (auto it = cldrViews.begin(); it != prunedEnd; ++it)
+            cldrList.emplace_back(it->toByteArray());
+        QList<QByteArray> joined;
+        joined.reserve(result.size() + cldrSize);
+        std::set_union(result.begin(), result.end(), cldrList.begin(), cldrList.end(),
+                       std::back_inserter(joined));
+        result = joined;
+    }
+
     return result;
 }
 
diff --git a/tests/auto/corelib/time/qtimezone/tst_qtimezone.cpp b/tests/auto/corelib/time/qtimezone/tst_qtimezone.cpp
index dfa5a8ccfd..c5745a1dcc 100644
--- a/tests/auto/corelib/time/qtimezone/tst_qtimezone.cpp
+++ b/tests/auto/corelib/time/qtimezone/tst_qtimezone.cpp
@@ -980,6 +980,11 @@ void tst_QTimeZone::availableTimeZoneIds()
         QCOMPARE_LT(list001.size(), listAll.size());
         QCOMPARE_LT(listUsa.size(), listAll.size());
         QCOMPARE_LT(listGmt.size(), listAll.size());
+        // And we do know CLDR data supplies some entries to each:
+        QCOMPARE_GT(listAll.size(), 0);
+        QCOMPARE_GT(list001.size(), 0);
+        QCOMPARE_GT(listUsa.size(), 0);
+        QCOMPARE_GT(listGmt.size(), 0);
     }
 }