Longacres was a Thoroughbred horse racetrack in Renton, Washington, United States. Owned by the Gottstein/Alhadeff family and operated by the Washington Jockey Club for the vast majority of its existence, the racetrack was the home of Thoroughbred racing in Western Washington from its opening in 1933 and was the longest continuously running track on the West Coast upon its closure. Until 1971, it was also the only place in Western Washington where gambling was legal. Notable races held at the racetrack include the Longacres Mile Handicap and the Gottstein Futurity.

After several years of losses due to increasing gambling and entertainment competition, the property was sold to Boeing in 1990. Boeing allowed the track to operate for two more years after the sale until the end of the 1992 season; the company demolished its structures in 1995. Boeing eventually built a new headquarters for its Commercial Airplanes division on the property along with a customer-training center; however, the company vacated the property and sold it in 2021 to Unico Partners. Seattle Sounders FC, in partnership with Unico, plans to renovate the site for use as a training facility; it is projected to open in January 2024.