Deer Park is a hamlet and census-designated place (CDP) in the Town of Babylon, in Suffolk County, on Long Island, in New York, United States.

Charles Wilson started what is now Deer Park in 1853 about eleven years after the Long Island Rail Road arrived in 1842-when he established a large and productive farm.

It was not until the effects of the post-World War II boom reached Deer Park that its economy ceased to be agricultural.

[4] Deer Park is reputed to have been the favorite summer spot of President John Quincy Adams, as his preferred vacation destination from 1835 until his death.

[6] According to the United States Census Bureau, the CDP has a total area of 6.2 square miles (16.0 km2), all land.

[7] It is bordered to the west by the Babylon hamlets of Wyandanch and Wheatley Heights, to the north by Dix Hills in the Town of Huntington, to the east by Brentwood and Baywood in the Town of Islip, and to the south by the hamlet of North Babylon.