diff --git a/src/corelib/CMakeLists.txt b/src/corelib/CMakeLists.txt
index ce3def3cd6..3707d5f886 100644
--- a/src/corelib/CMakeLists.txt
+++ b/src/corelib/CMakeLists.txt
@@ -897,7 +897,7 @@ qt_internal_extend_target(Core CONDITION QT_FEATURE_timezone AND UNIX AND NOT AN
 
 qt_internal_extend_target(Core
     CONDITION
-        QT_FEATURE_icu AND QT_FEATURE_timezone AND NOT ANDROID AND NOT APPLE
+        QT_FEATURE_icu AND QT_FEATURE_timezone AND NOT UNIX
     SOURCES
         time/qtimezoneprivate_icu.cpp
 )
diff --git a/src/corelib/configure.cmake b/src/corelib/configure.cmake
index 18c09d2241..83983dfa2e 100644
--- a/src/corelib/configure.cmake
+++ b/src/corelib/configure.cmake
@@ -860,7 +860,8 @@ qt_feature("timezone_locale" PRIVATE
     SECTION "Utilities"
     LABEL "QTimeZone"
     PURPOSE "Provides support for localized time-zone display names."
-    DISABLE ON # Implementation is currently incomplete, so leave turned off
+    CONDITION
+        QT_FEATURE_timezone AND ( ( UNIX AND NOT APPLE AND NOT ANDROID ) OR QT_FEATURE_icu )
 )
 qt_feature("datetimeparser" PRIVATE
     SECTION "Utilities"
diff --git a/src/corelib/time/qtimezonelocale.cpp b/src/corelib/time/qtimezonelocale.cpp
index 5757e55d28..cf3a84b317 100644
--- a/src/corelib/time/qtimezonelocale.cpp
+++ b/src/corelib/time/qtimezonelocale.cpp
@@ -4,7 +4,9 @@
 #include <private/qtimezonelocale_p.h>
 #include <private/qtimezoneprivate_p.h>
 
-#if !QT_CONFIG(icu) // Use data generated from CLDR:
+#if !QT_CONFIG(icu)
+#  include <private/qdatetime_p.h>
+// Use data generated from CLDR:
 #  include <private/qtimezonelocale_data_p.h>
 #  include <private/qtimezoneprivate_data_p.h>
 #endif
@@ -12,9 +14,90 @@
 QT_BEGIN_NAMESPACE
 
 #if QT_CONFIG(icu) // Get data from ICU:
+namespace {
+
+// Convert TimeType and NameType into ICU UCalendarDisplayNameType
+constexpr UCalendarDisplayNameType ucalDisplayNameType(QTimeZone::TimeType timeType,
+                                                       QTimeZone::NameType nameType)
+{
+    // TODO ICU C UCalendarDisplayNameType does not support full set of C++ TimeZone::EDisplayType
+    // For now, treat Generic as Standard
+    switch (nameType) {
+    case QTimeZone::OffsetName:
+        Q_UNREACHABLE(); // Callers of ucalTimeZoneDisplayName() should take care of OffsetName.
+    case QTimeZone::ShortName:
+        return timeType == QTimeZone::DaylightTime ? UCAL_SHORT_DST : UCAL_SHORT_STANDARD;
+    case QTimeZone::DefaultName:
+    case QTimeZone::LongName:
+        return timeType == QTimeZone::DaylightTime ? UCAL_DST : UCAL_STANDARD;
+    }
+    Q_UNREACHABLE_RETURN(UCAL_STANDARD);
+}
+
+} // nameless namespace
+
 namespace QtTimeZoneLocale {
 
+// Qt wrapper around ucal_getTimeZoneDisplayName()
+// Used directly by ICU backend; indirectly by TZ (see below).
+QString ucalTimeZoneDisplayName(UCalendar *ucal,
+                                QTimeZone::TimeType timeType,
+                                QTimeZone::NameType nameType,
+                                const QByteArray &localeCode)
+{
+    constexpr int32_t BigNameLength = 50;
+    int32_t size = BigNameLength;
+    QString result(size, Qt::Uninitialized);
+    auto dst = [&result]() { return reinterpret_cast<UChar *>(result.data()); };
+    UErrorCode status = U_ZERO_ERROR;
+    const UCalendarDisplayNameType utype = ucalDisplayNameType(timeType, nameType);
+
+    // size = ucal_getTimeZoneDisplayName(cal, type, locale, result, resultLength, status)
+    size = ucal_getTimeZoneDisplayName(ucal, utype, localeCode.constData(),
+                                       dst(), size, &status);
+
+    // If overflow, then resize and retry
+    if (size > BigNameLength || status == U_BUFFER_OVERFLOW_ERROR) {
+        result.resize(size);
+        status = U_ZERO_ERROR;
+        size = ucal_getTimeZoneDisplayName(ucal, utype, localeCode.constData(),
+                                           dst(), size, &status);
+    }
+
+    if (!U_SUCCESS(status))
+        return QString();
+
+    // Resize and return:
+    result.resize(size);
+    return result;
+}
+
 } // QtTimeZoneLocale
+
+// Used by TZ backends when ICU is available:
+QString QTimeZonePrivate::localeName(qint64 atMSecsSinceEpoch, int offsetFromUtc,
+                                     QTimeZone::TimeType timeType,
+                                     QTimeZone::NameType nameType,
+                                     const QLocale &locale) const
+{
+    Q_UNUSED(atMSecsSinceEpoch);
+    // TODO: use CLDR data for the offset name.
+    // No ICU API for offset formats, so fall back to our ISO one, even if
+    // locale isn't C:
+    if (nameType == QTimeZone::OffsetName)
+        return isoOffsetFormat(offsetFromUtc);
+
+    const QString id = QString::fromUtf8(m_id);
+    const QByteArray loc = locale.name().toUtf8();
+    UErrorCode status = U_ZERO_ERROR;
+    UCalendar *ucal = ucal_open(reinterpret_cast<const UChar *>(id.data()), id.size(),
+                                loc.constData(), UCAL_DEFAULT, &status);
+    if (ucal && U_SUCCESS(status)) {
+        auto tidier = qScopeGuard([ucal]() { ucal_close(ucal); });
+        return QtTimeZoneLocale::ucalTimeZoneDisplayName(ucal, timeType, nameType, loc);
+    }
+    return QString();
+}
 #else // No ICU, use QTZ[LP}_data_p.h data for feature timezone_locale.
 namespace {
 using namespace QtTimeZoneLocale; // QTZL_data_p.h
@@ -24,6 +107,20 @@ using namespace QtTimeZoneCldr; // QTZP_data_p.h
 // Accessors for the QTZP_data_p.h
 
 } // nameless namespace
+
+QString QTimeZonePrivate::localeName(qint64 atMSecsSinceEpoch, int offsetFromUtc,
+                                     QTimeZone::TimeType timeType,
+                                     QTimeZone::NameType nameType,
+                                     const QLocale &locale) const
+{
+    Q_ASSERT(nameType != QTimeZone::OffsetName || locale.language() != QLocale::C);
+    // Get data from QTZ[LP]_data_p.h
+
+    Q_UNUSED(atMSecsSinceEpoch);
+    Q_UNUSED(offsetFromUtc);
+    Q_UNUSED(timeType);
+    return QString();
+}
 #endif // ICU
 
 QT_END_NAMESPACE
diff --git a/src/corelib/time/qtimezonelocale_p.h b/src/corelib/time/qtimezonelocale_p.h
index adc8e83b35..6e6c6b51fd 100644
--- a/src/corelib/time/qtimezonelocale_p.h
+++ b/src/corelib/time/qtimezonelocale_p.h
@@ -14,18 +14,31 @@
 //
 // We mean it.
 //
+#include <private/qglobal_p.h>
 
+#include <QtCore/qstring.h>
 #include <QtCore/qtimezone.h>
 
+#if QT_CONFIG(icu)
+#include <unicode/ucal.h>
+#endif
+
 QT_REQUIRE_CONFIG(timezone);
 QT_REQUIRE_CONFIG(timezone_locale);
 
+QT_BEGIN_NAMESPACE
+
 namespace QtTimeZoneLocale {
 #if QT_CONFIG(icu)
+QString ucalTimeZoneDisplayName(UCalendar *ucal, QTimeZone::TimeType timeType,
+                                QTimeZone::NameType nameType,
+                                const QString &localeCode);
 #else
 // Define data types for QTZL_data_p.h
 
 #endif
 }
 
+QT_END_NAMESPACE
+
 #endif // QTIMEZONELOCALE_P_H
diff --git a/src/corelib/time/qtimezoneprivate.cpp b/src/corelib/time/qtimezoneprivate.cpp
index 6d522733aa..f3dc43df6a 100644
--- a/src/corelib/time/qtimezoneprivate.cpp
+++ b/src/corelib/time/qtimezoneprivate.cpp
@@ -5,6 +5,9 @@
 
 #include "qtimezone.h"
 #include "qtimezoneprivate_p.h"
+#if QT_CONFIG(timezone_locale)
+#  include "qtimezonelocale_p.h"
+#endif
 #include "qtimezoneprivate_data_p.h"
 
 #include <qdatastream.h>
@@ -181,7 +184,11 @@ QString QTimeZonePrivate::displayName(qint64 atMSecsSinceEpoch,
 
         QTimeZone::TimeType timeType
             = tran.daylightTimeOffset != 0 ? QTimeZone::DaylightTime : QTimeZone::StandardTime;
+#if QT_CONFIG(timezone_locale)
+        return localeName(atMSecsSinceEpoch, tran.offsetFromUtc, timeType, nameType, locale);
+#else
         return displayName(timeType, nameType, locale);
+#endif
     }
     return QString();
 }
@@ -190,10 +197,14 @@ QString QTimeZonePrivate::displayName(QTimeZone::TimeType timeType,
                                       QTimeZone::NameType nameType,
                                       const QLocale &locale) const
 {
-    if (nameType == QTimeZone::OffsetName && isDataLocale(locale)) {
-        const Data tran = data(timeType);
-        if (tran.atMSecsSinceEpoch != invalidMSecs())
+    const Data tran = data(timeType);
+    if (tran.atMSecsSinceEpoch != invalidMSecs()) {
+        if (nameType == QTimeZone::OffsetName && isDataLocale(locale))
             return isoOffsetFormat(tran.offsetFromUtc);
+
+#if QT_CONFIG(timezone_locale)
+        return localeName(tran.atMSecsSinceEpoch, tran.offsetFromUtc, timeType, nameType, locale);
+#endif
     }
     return QString();
 }
diff --git a/src/corelib/time/qtimezoneprivate_icu.cpp b/src/corelib/time/qtimezoneprivate_icu.cpp
index 1a3baa70d0..a9fe68b83c 100644
--- a/src/corelib/time/qtimezoneprivate_icu.cpp
+++ b/src/corelib/time/qtimezoneprivate_icu.cpp
@@ -4,6 +4,7 @@
 
 #include "qtimezone.h"
 #include "qtimezoneprivate_p.h"
+#include "qtimezonelocale_p.h"
 
 #include <unicode/ucal.h>
 
@@ -22,27 +23,6 @@ QT_BEGIN_NAMESPACE
 
 // ICU utilities
 
-// Convert TimeType and NameType into ICU UCalendarDisplayNameType
-static UCalendarDisplayNameType ucalDisplayNameType(QTimeZone::TimeType timeType, QTimeZone::NameType nameType)
-{
-    // TODO ICU C UCalendarDisplayNameType does not support full set of C++ TimeZone::EDisplayType
-    switch (nameType) {
-    case QTimeZone::ShortName :
-    case QTimeZone::OffsetName :
-        if (timeType == QTimeZone::DaylightTime)
-            return UCAL_SHORT_DST;
-        // Includes GenericTime
-        return UCAL_SHORT_STANDARD;
-    case QTimeZone::DefaultName :
-    case QTimeZone::LongName :
-        if (timeType == QTimeZone::DaylightTime)
-            return UCAL_DST;
-        // Includes GenericTime
-        return UCAL_STANDARD;
-    }
-    return UCAL_STANDARD;
-}
-
 // Qt wrapper around ucal_getDefaultTimeZone()
 static QByteArray ucalDefaultTimeZoneId()
 {
@@ -69,44 +49,6 @@ static QByteArray ucalDefaultTimeZoneId()
     return QByteArray();
 }
 
-// Qt wrapper around ucal_getTimeZoneDisplayName()
-static QString ucalTimeZoneDisplayName(UCalendar *ucal, QTimeZone::TimeType timeType,
-                                       QTimeZone::NameType nameType,
-                                       const QString &localeCode)
-{
-    int32_t size = 50;
-    QString result(size, Qt::Uninitialized);
-    UErrorCode status = U_ZERO_ERROR;
-
-    // size = ucal_getTimeZoneDisplayName(cal, type, locale, result, resultLength, status)
-    size = ucal_getTimeZoneDisplayName(ucal,
-                                       ucalDisplayNameType(timeType, nameType),
-                                       localeCode.toUtf8(),
-                                       reinterpret_cast<UChar *>(result.data()),
-                                       size,
-                                       &status);
-
-    // If overflow, then resize and retry
-    if (status == U_BUFFER_OVERFLOW_ERROR) {
-        result.resize(size);
-        status = U_ZERO_ERROR;
-        size = ucal_getTimeZoneDisplayName(ucal,
-                                           ucalDisplayNameType(timeType, nameType),
-                                           localeCode.toUtf8(),
-                                           reinterpret_cast<UChar *>(result.data()),
-                                           size,
-                                           &status);
-    }
-
-    // If successful on first or second go, resize and return
-    if (U_SUCCESS(status)) {
-        result.resize(size);
-        return result;
-    }
-
-    return QString();
-}
-
 // Qt wrapper around ucal_get() for offsets
 static bool ucalOffsetsAtTime(UCalendar *m_ucal, qint64 atMSecsSinceEpoch,
                               int *utcOffset, int *dstOffset)
@@ -203,13 +145,11 @@ static QTimeZonePrivate::Data ucalTimeZoneTransition(UCalendar *m_ucal,
     tran.offsetFromUtc = utc + dst;
     tran.standardTimeOffset = utc;
     tran.daylightTimeOffset = dst;
-    // TODO No ICU API, use short name instead
-    if (dst == 0)
-        tran.abbreviation = ucalTimeZoneDisplayName(m_ucal, QTimeZone::StandardTime,
-                                                    QTimeZone::ShortName, QLocale().name());
-    else
-        tran.abbreviation = ucalTimeZoneDisplayName(m_ucal, QTimeZone::DaylightTime,
-                                                    QTimeZone::ShortName, QLocale().name());
+    // TODO No ICU API, use short name as abbreviation.
+    QTimeZone::TimeType timeType = dst == 0 ? QTimeZone::StandardTime : QTimeZone::DaylightTime;
+    using namespace QtTimeZoneLocale;
+    tran.abbreviation = ucalTimeZoneDisplayName(m_ucal, timeType,
+                                                QTimeZone::ShortName, QLocale().name());
     return tran;
 }
 #endif // U_ICU_VERSION_SHORT
@@ -317,6 +257,7 @@ QString QIcuTimeZonePrivate::displayName(QTimeZone::TimeType timeType,
     }
     // Technically this may be suspect, if locale isn't QLocale(), since that's
     // what we used when constructing m_ucal; does ICU cope with inconsistency ?
+    using namespace QtTimeZoneLocale;
     return ucalTimeZoneDisplayName(m_ucal, timeType, nameType, locale.name());
 }
 
diff --git a/src/corelib/time/qtimezoneprivate_p.h b/src/corelib/time/qtimezoneprivate_p.h
index e0632e7cec..5d57ed7558 100644
--- a/src/corelib/time/qtimezoneprivate_p.h
+++ b/src/corelib/time/qtimezoneprivate_p.h
@@ -152,6 +152,15 @@ public:
         return QByteArrayLiteral("UTC");
     }
 
+#if QT_CONFIG(timezone_locale)
+private:
+    // Defined in qtimezonelocale.cpp
+    QString localeName(qint64 atMSecsSinceEpoch, int offsetFromUtc,
+                       QTimeZone::TimeType timeType,
+                       QTimeZone::NameType nameType,
+                       const QLocale &locale) const;
+#endif // L10n helpers.
+
 protected:
     QByteArray m_id;
 };
@@ -223,7 +232,7 @@ private:
 // TODO: shuffle (almost reverse) order of and rework #if-ery here to use #elif
 // and match the #if-ery in each of QTZ's newBackendTimeZone() cascades for
 // backend selection.
-#if QT_CONFIG(icu)
+#if QT_CONFIG(icu) && !defined(Q_OS_UNIX)
 class Q_AUTOTEST_EXPORT QIcuTimeZonePrivate final : public QTimeZonePrivate
 {
 public:
@@ -266,7 +275,7 @@ private:
 
     UCalendar *m_ucal;
 };
-#endif // ICU
+#endif // ICU not on Unix.
 
 #if defined(Q_OS_UNIX) && !defined(Q_OS_DARWIN) && !defined(Q_OS_ANDROID)
 struct QTzTransitionTime
@@ -347,14 +356,6 @@ private:
 
     Data dataForTzTransition(QTzTransitionTime tran) const;
     Data dataFromRule(QTzTransitionRule rule, qint64 msecsSinceEpoch) const;
-#if QT_CONFIG(icu)
-# ifdef __cpp_lib_is_final
-    static_assert(std::is_final<QIcuTimeZonePrivate>::value,
-                  "if QIcuTimeZonePrivate isn't final, we may need to specialize "
-                  "QExplicitlySharedDataPointer::clone() to call QTimeZonePrivate::clone()");
-# endif
-    mutable QExplicitlySharedDataPointer<const QIcuTimeZonePrivate> m_icu;
-#endif
     QTzTimeZoneCacheEntry cached_data;
     const QList<QTzTransitionTime> &tranCache() const { return cached_data.m_tranTimes; }
 };
diff --git a/src/corelib/time/qtimezoneprivate_tz.cpp b/src/corelib/time/qtimezoneprivate_tz.cpp
index d057dae37f..8d14e75193 100644
--- a/src/corelib/time/qtimezoneprivate_tz.cpp
+++ b/src/corelib/time/qtimezoneprivate_tz.cpp
@@ -33,10 +33,6 @@ QT_BEGIN_NAMESPACE
 
 using namespace Qt::StringLiterals;
 
-#if QT_CONFIG(icu)
-Q_CONSTINIT static QBasicMutex s_icu_mutex;
-#endif
-
 /*
     Private
 
@@ -771,9 +767,6 @@ QTzTimeZonePrivate::~QTzTimeZonePrivate()
 
 QTzTimeZonePrivate *QTzTimeZonePrivate::clone() const
 {
-#if QT_CONFIG(icu)
-    const auto lock = qt_scoped_lock(s_icu_mutex);
-#endif
     return new QTzTimeZonePrivate(*this);
 }
 
@@ -1007,15 +1000,7 @@ QTzTimeZonePrivate::QTzTimeZonePrivate(const QByteArray &ianaId)
     if (m_id.isEmpty()) {
         // This can only happen for the system zone, when we've read the
         // contents of /etc/localtime because it wasn't a symlink.
-#if QT_CONFIG(icu)
-        // Use ICU's system zone, if only to avoid using the abbreviation as ID
-        // (ICU might mis-recognize it) in displayName().
-        m_icu = new QIcuTimeZonePrivate();
-        // Use its ID, as an alternate source of data:
-        m_id = m_icu->id();
-        if (!m_id.isEmpty())
-            return;
-#endif
+        // TODO: use CLDR generic abbreviation for the zone.
         m_id = abbreviation(QDateTime::currentMSecsSinceEpoch()).toUtf8();
     }
 }
@@ -1034,18 +1019,6 @@ QString QTzTimeZonePrivate::displayName(QTimeZone::TimeType timeType,
                                         QTimeZone::NameType nameType,
                                         const QLocale &locale) const
 {
-    // TZ DB lacks localized names (it only has IANA IDs), so delegate to ICU
-    // for those, when available.
-#if QT_CONFIG(icu)
-    {
-        auto lock = qt_scoped_lock(s_icu_mutex);
-        // TODO Some valid TZ names are not valid ICU names, use translation table?
-        if (!m_icu)
-            m_icu = new QIcuTimeZonePrivate(m_id);
-        if (m_icu->isValid())
-            return m_icu->displayName(timeType, nameType, locale);
-    }
-#endif
     // TZ only provides C-locale abbreviations and offset:
     if (nameType != QTimeZone::LongName && isDataLocale(locale)) {
         QTimeZonePrivate::Data tran = data(timeType);
@@ -1057,7 +1030,7 @@ QString QTzTimeZonePrivate::displayName(QTimeZone::TimeType timeType,
                 return isoOffsetFormat(tran.offsetFromUtc);
         }
     }
-    // Otherwise, fall back to base class:
+    // Otherwise, fall back to base class (and qtimezonelocale.cpp):
     return QTimeZonePrivate::displayName(timeType, nameType, locale);
 }
 
diff --git a/tests/auto/corelib/time/qtimezone/tst_qtimezone.cpp b/tests/auto/corelib/time/qtimezone/tst_qtimezone.cpp
index d2e8f63f24..7f6bc96aa6 100644
--- a/tests/auto/corelib/time/qtimezone/tst_qtimezone.cpp
+++ b/tests/auto/corelib/time/qtimezone/tst_qtimezone.cpp
@@ -1280,7 +1280,7 @@ void tst_QTimeZone::utcTest()
 
 void tst_QTimeZone::icuTest()
 {
-#if defined(QT_BUILD_INTERNAL) && QT_CONFIG(icu)
+#if defined(QT_BUILD_INTERNAL) && QT_CONFIG(icu) && !defined(Q_OS_UNIX)
     // Known datetimes
     qint64 std = QDateTime(QDate(2012, 1, 1), QTime(0, 0), QTimeZone::UTC).toMSecsSinceEpoch();
     qint64 dst = QDateTime(QDate(2012, 6, 1), QTime(0, 0), QTimeZone::UTC).toMSecsSinceEpoch();
@@ -1323,7 +1323,7 @@ void tst_QTimeZone::icuTest()
     if (QTest::currentTestFailed())
         return;
     testEpochTranPrivate(QIcuTimeZonePrivate("America/Toronto"));
-#endif // icu
+#endif // ICU not on Unix
 }
 
 void tst_QTimeZone::tzTest()
@@ -1527,7 +1527,7 @@ void tst_QTimeZone::tzTest()
         QDateTime dt(QDate(2016, 3, 28), QTime(0, 0), UTC);
         QCOMPARE(tzBarnaul.data(dt.toMSecsSinceEpoch()).abbreviation, QString("+07"));
     }
-#endif // QT_BUILD_INTERNAL && Q_OS_UNIX && !Q_OS_DARWIN
+#endif // QT_BUILD_INTERNAL && Q_OS_UNIX && !Q_OS_DARWIN && !Q_OS_ANDROID
 }
 
 void tst_QTimeZone::macTest()