Mission San Buenaventura, formally known as the Mission Basilica of San Buenaventura, is a Catholic parish and basilica in the Archdiocese of Los Angeles. The parish church in the city of Ventura, California, United States, is a Spanish mission founded by the Order of Friars Minor. Founded on March 31, 1782, it was the ninth Spanish mission established in Alta California and the last to be established by the head of the Franciscan missions in California, Junípero Serra. Designated a California Historical Landmark, the mission is one of many locally designated landmarks in downtown Ventura.

Ventura, officially named San Buenaventura, is a city in and the county seat of Ventura County, California, United States. It is a coastal city located northwest of Los Angeles. The population was 110,763 at the 2020 census. Ventura is a popular tourist destination, owing to its historic landmarks, beaches, and resorts.