diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 5d5b8e415f3cd2..65c034c054a17a 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -5661,6 +5661,37 @@ def test_astimezone_default_near_fold(self):
         s = t.astimezone()
         self.assertEqual(t.tzinfo, s.tzinfo)
 
+    @unittest.skipIf(sys.platform != "win32", "gh-148658 only affects Windows")
+    def test_astimezone_negative_timestamp_dst(self):
+        # gh-148658: astimezone() returned incorrect DST name for negative
+        # timestamps on Windows. Verify C layer returns correct tm_zone
+        # by checking astimezone() produces correct timezone names.
+        import time
+        winter_ts = -1  # 1969-12-31
+        summer_ts = -15897600  # 1969-07-01
+
+        # Get expected timezone names from time.localtime
+        winter_local = time.localtime(winter_ts)
+        summer_local = time.localtime(summer_ts)
+
+        dt_winter = self.theclass.fromtimestamp(winter_ts).astimezone()
+        dt_summer = self.theclass.fromtimestamp(summer_ts).astimezone()
+
+        # Verify astimezone() returns correct timezone names
+        self.assertEqual(dt_winter.tzname(), winter_local.tm_zone)
+        self.assertEqual(dt_summer.tzname(), summer_local.tm_zone)
+
+        # For DST timezones, winter and summer should have different names
+        # For non-DST timezones, names should be the same
+        if winter_local.tm_zone == summer_local.tm_zone:
+            # Non-DST timezone: both should be standard time
+            self.assertEqual(winter_local.tm_isdst, 0)
+            self.assertEqual(summer_local.tm_isdst, 0)
+        else:
+            # DST timezone: one should be standard, one DST
+            self.assertEqual(winter_local.tm_isdst, 0)
+            self.assertEqual(summer_local.tm_isdst, 1)
+
     def test_aware_subtract(self):
         cls = self.theclass
 
diff --git a/Misc/NEWS.d/next/Windows/2026-04-17-19-42-04.gh-issue-148658.yhgT1z.rst b/Misc/NEWS.d/next/Windows/2026-04-17-19-42-04.gh-issue-148658.yhgT1z.rst
new file mode 100644
index 00000000000000..f2b37ef0e1ec93
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2026-04-17-19-42-04.gh-issue-148658.yhgT1z.rst
@@ -0,0 +1 @@
+Fix DST timezone name for negative timestamps on Windows.
diff --git a/Python/pytime.c b/Python/pytime.c
index 399ff59ad01ab6..2bd20ac38f11d3 100644
--- a/Python/pytime.c
+++ b/Python/pytime.c
@@ -10,6 +10,7 @@
 #endif
 #ifdef MS_WINDOWS
 #  include <winsock2.h>           // struct timeval
+#  include <windows.h>            // time zone APIs
 #endif
 
 #if defined(__APPLE__)
@@ -355,8 +356,43 @@ _PyTime_windows_filetime(time_t timer, struct tm *tm, int is_local)
     // `time.gmtime` and `time.localtime` will return `struct_time` containing this
     tm->tm_yday = _PyTime_calc_yday(&st_result);
 
-    /* DST flag: -1 (unknown) for local time on historical dates, 0 for UTC */
-    tm->tm_isdst = is_local ? -1 : 0;
+    /* DST flag: -1 (unknown) for local time on historical dates, 0 for UTC.
+     * Detect DST by comparing standard time with local time (gh-148658). */
+    if (is_local) {
+        TIME_ZONE_INFORMATION tzi;
+        DWORD tz_result = GetTimeZoneInformation(&tzi);
+        if (tz_result == TIME_ZONE_ID_INVALID ||
+            tzi.DaylightDate.wMonth == 0) {
+            /* Timezone does not observe DST */
+            tm->tm_isdst = 0;
+        }
+        else {
+            /* Calculate standard time from UTC and compare with local time. */
+            ULONGLONG utc_ticks = ((ULONGLONG)timer + SECS_BETWEEN_EPOCHS) *
+                                   HUNDRED_NS_PER_SEC;
+            LONGLONG standard_offset_ticks = (LONGLONG)tzi.Bias * 60LL *
+                                              HUNDRED_NS_PER_SEC;
+            ULONGLONG standard_ticks = utc_ticks - standard_offset_ticks;
+            FILETIME ft_standard;
+            ft_standard.dwLowDateTime = (DWORD)(standard_ticks);
+            ft_standard.dwHighDateTime = (DWORD)(standard_ticks >> 32);
+            SYSTEMTIME st_standard;
+            if (!FileTimeToSystemTime(&ft_standard, &st_standard)) {
+                PyErr_SetFromWindowsErr(0);
+                return -1;
+            }
+            if (st_result.wHour == st_standard.wHour &&
+                st_result.wMinute == st_standard.wMinute) {
+                tm->tm_isdst = 0;
+            }
+            else {
+                tm->tm_isdst = 1;
+            }
+        }
+    }
+    else {
+        tm->tm_isdst = 0;
+    }
 
     return 0;
 }