South Bass Island is a small island in western Lake Erie, and a part of Ottawa County, Ohio, United States. It is the southernmost of the three Bass Islands and located 3 miles (4.6 km) from the south shore of Lake Erie. It is the third largest island in the Lake Erie Islands, and is part of Put-in-Bay Township. In the bay of South Bass is Gibraltar Island, home to the Ohio State University's Stone Laboratory.
The island is a popular recreation spot and is often referred to as the "Key West of Lake Erie." The village of Put-in-Bay is a popular tourist destination during the summer. It is served by ferry from nearby Port Clinton and Sandusky, both on the mainland. The island is the annual host of the Inter-Lake Yachting Association regatta, known as Bay Week.
Perry's Victory and International Peace Memorial, including Perry's Monument, commemorates the Battle of Lake Erie, which the United States won during the War of 1812. It is located on South Bass Island, near Put-In-Bay.