|Primary inflows||Steinbach or Ostersee-Ach|
|Catchment area||314 km2 (121 sq mi)|
|Max. length||20.2 km (12.6 mi)|
|Surface area||58.36 km2 (22.53 sq mi)|
|Max. depth||127.8 m (419 ft)|
|Water volume||2,998×106 m3 (105.9×109 cu ft)|
|Residence time||21 years|
|Surface elevation||596 m (1,955 ft)|
|Settlements||Starnberg, Ammerland, Seeshaupt, Tutzing, Feldafing, Possenhofen|
Lake Starnberg (German: Starnberger See, German pronunciation (help·info)) — called Lake Würm (German Würmsee) until 1962 — is Germany's fifth largest freshwater lake in terms of area and, due to its great average depth, the second largest in terms of water volume, after Lake Constance. The lake and its surroundings are an unincorporated area within the rural district of Starnberg; the lake itself is the property of the state of Bavaria and is administered by the Bavarian Administration of State-Owned Palaces, Gardens and Lakes.
Located in southern Bavaria 25 kilometres (16 mi) southwest of Munich, Lake Starnberg is a popular recreation area for the city and, since 1976, one of the wetlands of international importance protected by the Ramsar Convention. The small town of Berg is famous as the site where King Ludwig II of Bavaria was found dead in the lake in 1886. Because of its associations with the Wittelsbach royal family, the lake is also known as Fürstensee (Prince's Lake). It is also mentioned in T. S. Eliot's poem The Waste Land.
The lake, lying in a zungenbecken or glacial hollow, was created by ice age glaciers from the Alps, and extends 21 km (13 mi) from north to south and has a width of 3–5 km (2-3.5 miles) from east to west. It has a single small island, the Roseninsel, and a single outlet, the Würm river (because of this river the lake was called the Würmsee until 1962). Its major inflow comes from a small river called the Steinbach or Ostersee-Ach, which flows through a chain of small lakes to the south, the Osterseen. The lake's water is of excellent quality due to the introduction in the 1960s of a circular sewerage system which collects wastewater from the settlements around the lake and transports it to a treatment plant below the lake's outlet at Starnberg. Bronze fish-hooks and a dugout dating to the 9th or 8th century BCE have been discovered at the lake, and there are still some professional fishers, most of them continuing a family tradition.
Hikers and cyclists can circumnavigate the lake using a path approximately 49 kilometres (30 mi) long. Access to the lakeshore is not everywhere possible, since it is mostly private property. Passenger ferries and excursion ships have operated on the lake since 1851. Today they are operated by the Bayerische Seenschifffahrt company, using modern engine-driven ships.
The earliest surviving mention of the lake, as Uuirmseo, is in an 818 document referring to Holzhausen, now part of Münsing. This name became Wirmsee, already recorded during the reign of the Holy Roman Emperor Louis the Bavarian (1314–1347). This name is derived from the Wirm, now spelt Würm, the only river which flows out of the lake, at Starnberg; in the 19th century, the spellings were changed to Würm and Würmsee.
In the late 19th century, a railway connection between Munich and Starnberg made the lake an accessible destination for trips from the city. Trains departed from a wing of the Munich Central Station which was known as the 'Starnberg branch station' (Starnberger Flügelbahnhof) and the lake came increasingly to be known as Lake Starnberg; its name was finally officially changed in 1962.
Clockwise from the north, the following settlements abut the lake:
- Starnberg (North, Starnberg district)
- Berg (North East, Starnberg district): including Kempfenhausen, Berg and Leoni
- Münsing (South East, Bad Tölz-Wolfratshausen district): including Ammerland, Ambach, Pischetsrieder and St. Heinrich
- Seeshaupt (South, Weilheim-Schongau district): including Seeseiten
- Bernried (South West, Weilheim-Schongau district)
- Tutzing (West, Starnberg district): including Unterzeismering; Evangelische Akademie Tutzing on the lake
- Feldafing (North West, Starnberg district): including Garatshausen
- Pöcking (North West, Starnberg district): including Possenhofen and Niederpöcking
- Bayregio. "The lake Starnberger See". BAYregio-Starnberger-See.de. Archived from the original on 10 August 2011. Retrieved 8 August 2011.
- "Bayerische Seenschifffahrt". Bayerische Seenschifffahrt. Retrieved 2011-07-11.
- "Geschichtliche Hintergründe" [Historical Background] (in German). Bayerische Seenschifffahrt. Archived from the original on 2011-12-10. Retrieved 2011-07-11.
- Würmsee, in: Arbeitskreis für Ortsgeschichteforschung der Würmregion, Materialien zur Ortsgeschichtsforschung in der Würmregion, Gauting 2001, p. 245.
- Bayerische Staatsbibliothek, S. 289, Regesten Kaiser Ludwigs des Bayern - Die Urkunden aus Klöstern und Stiftsarchiven im Bayerischen Hauptstaatsarchiv und in der Bayerischen Staatsbibliothek, ed. Menzel, 1996 (in German) [https://www.webcitation.org/1312942211056220?url=http://regesta-imperii.digitale-sammlungen.de/regest/ri07_ri_1341-02-05_000002_000001_007_001_003_000638_0000000638 Archived August 10 2011, at WebCite
- Martinus Fesq-Martin, Amei Lang and Michael Peters (Eds.). Der Starnberger See—Natur und Vorgeschichte einer bayerischen Landschaft. Munich, 2008. ISBN 978-3-89937-090-4 (in German)
- A. Link. Der Starnberger See und seine Umgebung vom Würmtal bis zum Alpenrand. Gauting-Buchendorf, 1982. ISBN 3-923657-06-4 (in German)
- Susanne Westendorf. Das Starnberger-SeeBuch—eine Tour um den See, kleiner Führer. Munich, 1995. ISBN 3-00-000232-4 (in German)
- Lorenz von Westenrieder. Beschreibung des Wurm- oder Starenbergersees und der umherliegenden Schlösser, samt einer Landkarte. 1783, repr. Dachau: Bayerland, 2006. ISBN 3-89251-367-8 (in German)
- Oskar Weber and Josef Wahl. Am Starnberger See und die Würm entlang. Dachau, 1995. ISBN 3-89251-202-7 (in German)
- Media related to Lake Starnberg at Wikimedia Commons
- Nixdorf, B.; et al. (2004), "Starnberger See", Dokumentation von Zustand und Entwicklung der wichtigsten Seen Deutschlands (in German), Berlin: Umweltbundesamt, p. 75
- Pictures of Lake Starnberg