Oakdale is a hamlet (and census-designated place) in Suffolk County, New York, United States. The population was 7,974 at the 2010 census. Oakdale is in the Town of Islip. It has been home to Gilded Age mansions, the South Side Sportsmen's Club, and the main campus of Dowling College. It is now home to Connetquot River State Park Preserve.
Oakdale was founded around two Native American trade routes, where Sunrise Highway and Montauk Highway currently lie. Oakdale was part of the royal land grant given to William Nicoll, who founded Islip Town in 1697. Local historian Charles P. Dickerson wrote in 1975 that Oakdale's name appeared to come from a Nicoll descendant in the mid-19th century. The community includes: St. John's Episcopal Church, built in 1765, is the third oldest church on Long Island.