Bainbridge Island is a city and island in Kitsap County, Washington, United States, located in Puget Sound. The population was 23,025 at the 2010 census and an estimated 25,298 in 2019, 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.