Greifswald (German pronunciation: [ˈɡʁaɪfsvalt] ^ⓘ; Low German: Griepswold), officially the University and Hanseatic City of Greifswald (German: Universitäts- und Hansestadt Greifswald) is the fourth-largest city in the German state of Mecklenburg-Western Pomerania after Rostock, Schwerin and Neubrandenburg. In 2021 it surpassed Stralsund for the first time, and became the largest city in the Pomeranian part of the state. It sits on the River Ryck, at its mouth into the Danish Wiek, a sub-bay of the Bay of Greifswald, which is itself a sub-bay of the Bay of Pomerania of the Baltic Sea.

It is the seat of the district of Western Pomerania-Greifswald, and is located roughly in the middle between the two largest Pomeranian islands of Rügen and Usedom. The closest larger cities are Stralsund, Rostock, Szczecin and Schwerin. It lies west of the River Zarow, the historical cultural and linguistic boundary between West (west of the river) and Central Pomerania (east of the river). The city derives its name from the dukes of Pomerania, the House of Griffin, and thus ultimately from the Pomeranian Griffin, and its name hence translates as "Griffin's Forest".

The University of Greifswald, which was founded in 1456, is the second-oldest university in the Baltic Region after the University of Rostock. The city is well-known for the ruins of Eldena Abbey (formerly Hilda Abbey), a frequent subject of the paintings of Caspar David Friedrich, who was born in the city when it was part of Swedish Pomerania. Greifswald is the seat of the Pomeranian State Museum (Pommersches Landesmuseum). The recently built Ryck Barrier (Rycksperrwerk) protects the city from exceptionally high tides and storm surges moving up from the Baltic.

The city's population was listed at 59,332 in 2021, including many of the 12,500 students and 5,000 employees of the University of Greifswald. Greifswald draws international attention due to the university, its surrounding BioCon Valley, the Nord Stream 1 gas pipeline which ends at nearby Lubmin, and the Wendelstein 7-X nuclear fusion projects.

Greifswald is located in the northeast of Germany, approximately equidistant from Germany's two largest islands, Rügen and Usedom. The city is situated at the south end of the Bay of Greifswald, the historic centre being about five kilometres (three miles) up the river Ryck that crosses the city. The area around Greifswald is mainly flat, and hardly reaches more than 20 m above sea level. Two islands, Koos and Riems, are also part of Greifswald. Three of Germany's fourteen national parks can be reached by car in one hour or less from Greifswald.

Greifswald is also roughly equidistant from Germany's two largest cities, Berlin (240 km or 150 mi) and Hamburg (260 km or 160 mi). The nearest larger cities are Stralsund and Rostock.

The coastal part of Greifswald at the mouth of the Ryck, named Greifswald-Wieck, evolved from a fishing village. Today it provides a small beach, a marina and the main port for Greifswald.

Greifswald features an oceanic climate with some humid continental influence. Summers are pleasantly warm, although chilly at night. Due to its coastal location, heatwaves in Greifswald tend to be less extreme than other nearby locations inland. Winters are mild to cold, with occasional cold fronts coming in from Scandinavia or Siberia. Precipitation is spread throughout the year and comparatively low by German standards, while sunshine hours are above the German average.