Bainbridge Island is located within the Puget Sound Basin, east of the Kitsap Peninsula, directly east of the Manette Peninsula and west of the city of Seattle. The island is approximately 5 miles (8 km) wide and 10 miles (16 km) long, encompassing nearly 17,778 acres (27.778 sq mi; 71.95 km2), and is one of the larger islands in Puget Sound.
Bainbridge Island shorelines border the main body of Puget Sound, as well as Port Orchard Bay, a large protected embayment, and two high-current tidal passages, Rich Passage and Agate Pass. The island is characterized by an irregular coastline of approximately 53 miles (85 km), with numerous bays and inlets and a significant diversity of other coastal land forms, including spits, bluffs, dunes, lagoons, cuspate forelands, tombolos, tide flats, streams and tidal deltas, islands, and rocky outcrops. The high point is 425-foot (130 m) Toe Jam Hill.
The island is quite hilly and is known for its popular Chilly Hilly bicycle ride every February. This ride has been the unofficial start to the bicycling season in the Pacific Northwest since 1975.
Bainbridge Island is connected to the Kitsap Peninsula by the Agate Pass Bridge, carrying SR 305 over Agate Passage. The only other public way off the island is by the Seattle–Bainbridge ferry, the Washington State Ferries service from the dock at Winslow in Eagle Harbor to Colman Dock (Pier 52) in Seattle.