Mission Bay is a salt-water bay or lagoon located south of the Pacific Beach community of San Diego, California. The bay is part of the recreational Mission Bay Park, which is the largest man-made aquatic park in the country, consisting of 4,235 acres, approximately 46% land and 54% water. The combined area makes Mission Bay Park the ninth largest municipally-owned park in the United States.

Wakeboarding, jet skiing, sailing, and camping are popular on the bay. With miles of light color sandy beaches and an equally long pedestrian path, it is equally suitable for cycling, jogging or sunbathing.

Fiesta Island, a large peninsular park located within Mission Bay, is a popular location for charity walks and runs, bicycle races, time trials and other special events. It is also the home of the annual Over-the-line tournament.

Mission Bay is also host to the annual Bayfair Cup, which is a hydroplane boat race that takes place on the H1 Unlimited circuit.