Ada is a city in and the county seat of Pontotoc County, Oklahoma, United States. The population was 16,008 at the 2000 census. As of 2009, the city population was estimated at 17,019.
Ada is an Oklahoma Main Street City, an Oklahoma Certified City, a Tree City USA member, and a National Weather Service StormReady Community.
The city was named after the daughter of an early settler. It was incorporated in 1901. Ada is home to East Central University.