Bainbridge Island is a city and island in Kitsap County, Washington, United States. It is located in Puget Sound. The population was 24,825 at the 2020 census, making Bainbridge Island the second largest city in Kitsap County.

The island is separated from the Kitsap Peninsula by Port Orchard, with Bremerton lying to the southwest. Bainbridge Island is a suburb of Seattle, connected via the Washington State Ferries system and to Poulsbo and the Suquamish Indian Reservation by State Route 305, which uses the Agate Pass Bridge.

For thousands of years, members of the Suquamish people and their ancestors lived on the land now called Bainbridge Island. There were nine villages on the island; these included winter villages at Port Madison, Battle Point, Point White, Lynwood Center, Port Blakely, and Eagle Harbor, as well as summer villages at Manzanita, Fletcher Bay, and Rolling Bay.

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 wide and 10 miles long, encompassing nearly 17,778 acres, and is one of the larger islands in Puget Sound.