Rügen is Germany's largest island. It is located off the Pomeranian coast in the Baltic Sea and belongs to the state of Mecklenburg-Vorpommern. The "gateway" to Rügen island is the Hanseatic city of Stralsund, where it is linked to the mainland by road and railway via the Rügen Bridge and Causeway, two routes crossing the two-kilometre-wide Strelasund, a sound of the Baltic Sea.

Rügen has a maximum length of 51.4 km (31.9 mi) (from north to south), a maximum width of 42.8 km (26.6 mi) in the south and an area of 926 km2 (358 sq mi). The coast is characterized by numerous sandy beaches, lagoons (Bodden) and open bays (Wieke), as well as projecting peninsulas and headlands. In June 2011, UNESCO awarded the status of a World Heritage Site to the Jasmund National Park, famous for its vast stands of beeches and chalk cliffs like King's Chair, the main landmark of Rügen island.

The island of Rügen is part of the district of Vorpommern-Rügen, with its county seat in Stralsund.

The towns on Rügen are: Bergen, Sassnitz, Putbus and Garz. In addition, there are the Baltic seaside resorts of Binz, Baabe, Göhren, Sellin and Thiessow.

Rügen is very popular as a tourist destination because of its resort architecture, the diverse landscape and its long, sandy beaches.

Rügen, together with the Danish island of Møn on the far side of Rügen in the Baltic Sea and the area around Dover, England, once belonged to a large chalk plateau, which had been pushed by tectonic movements to the earth's surface. The vast majority of this land mass has disappeared as a result of erosion and faulting, leaving the two islands with their characteristic white chalk cliffs.

The main body of the island, known as Muttland, is surrounded by several peninsulas. To the north lie the peninsulas of Wittow and Jasmund, connected to each other by the Schaabe sandbar and to Muttland by the Schmale Heide, an embankment at Lietzow and the Wittow Ferry. The northern peninsulas are separated from Muttland by several lagoons or bodden, the largest of which are the Großer Jasmunder Bodden and Kleiner Jasmunder Bodden. Major peninsulas in the south are Zudar and Mönchgut which both face the Bay of Greifswald.

The northern part of the Bay of Greifswald, the Rügischer Bodden, is a large bay in the south of Rügen island, with the island of Vilm lying just offshore. At the western end of the bay, the peninsula of Zudar runs out to the southernmost point of Rügen (Palmer Ort), at the eastern end the highly indented peninsula of Mönchgut projects into the sea. This peninsula ends in the east at the cape of Nordperd near Göhren and in the south at the cape of Südperd by Thiessow. In the west of the peninsula of Mönchgut a narrow, 5 km (3.1 mi)-long bar, the Reddevitz Höft, separates the two bays of Having and Hagensche Wiek.

In the north-east of the island of Rügen is formed by the peninsula of Jasmund, which is joined to the heart of the island, Muttland, by the bar of Schmale Heide between Binz-Prora and Sassnitz-Mukran and by a rail and road embankment at Lietzow. The Schmale Heide separates the outer bay of Prorer Wiek from the lagoon of the Kleiner Jasmunder Bodden. On the peninsula of Jasmund are the Piekberg (161 m above sea level (NN)), the highest point on Rügen, and the Königsstuhl, a 118-metre (387 ft)-high chalk cliff in Stubbenkammer, which forms the most striking landmark on the island. Another bar, the Schaabe, links Jasmund to the peninsula of Wittow in the north of Rügen. The Schaabe, in turn, separates the outer bay of Tromper Wiek from the lagoon of the Großer Jasmunder Bodden. The peninsula of Wittow and the long, narrow peninsula of Bug to the west are separated from the main body of Rügen by the Rassower Strom, the Breetzer Bodden and the Breeger Bodden. The Wittow peninsula is adjoined in the north by Cape Arkona. Just under a kilometre to the northwest, located at 54°41' N, is the northernmost point of Mecklenburg-Western Pomerania. Below this cliff (Gellort) on the shoreline is the Siebenschneiderstein - the fourth largest glacial erratic boulder on Rügen.

The northwestern and western sides of Rügen are also highly indented, but a little flatter. Offshore are the larger islands of Hiddensee and Ummanz as well as the smaller islands Öhe Liebitz and Heuwiese. Sand removal and deposition by the Baltic Sea has to be constantly countered by dredging operations to the north and south of Hiddensee, otherwise Hiddensee would merge with Rügen within a few years. Rügen is dotted with many glacial erratic boulders, of which the 22 largest belong to legally-protected geotopes (see also: Erratics on and around Rügen).