Bay Shore is a hamlet and census-designated place (CDP) in the Town of Islip, Suffolk County, New York, United States. It is situated on the South Shore of Long Island, adjoining the Great South Bay. In 2008, Bay Shore celebrated the 300th anniversary of the purchase of the land from the Secatogue Native Americans. The population of the CDP was 26,337 at the time of the 2010 census.
Bay Shore is one of the older hamlets on Long Island. Sagtikos Manor, located in West Bay Shore, was built around 1697. It was used as a British armed forces headquarters, at the time of the Battle of Long Island during the Revolutionary War. President Washington stayed at the manor during his tour of Long Island in 1790.
The land that would become Bay Shore proper was purchased from the Secatogue Native Americans in 1708 by local school teacher John Mowbray for "several eel spears".
The hamlet's name has changed over time: Early European settlers referred to the area first as Penataquit and later as Awixa; both were names used by the Native American Secatogue tribe. For reasons never documented, the name was changed in the early 19th century to Sodom. In 1842 there was a further name change to Mechanicsville, then a return in 1849 to Penataquit.