Mission Beach is a community built on a sandbar between the Pacific Ocean and Mission Bay. It is part of the city of San Diego, California.

Mission Beach spans nearly two miles of ocean front. It is bounded by the San Diego River estuary on the south, Mission Bay Park on the east, and the community of Pacific Beach on the north. A boardwalk runs along the beaches on both the ocean and bay sides of the community. The main artery through Mission Beach is Mission Boulevard. The community is divided into South Mission and North Mission. At the south end of the beach on the ocean side is a jetty; on the bay side is a park with grass, parking and a walking path.

Many residential structures in Mission Beach were built in the 1930s and '40s as summer cottages and some date as early as the 1920s. The rare airplane bungalow on Manhattan Court was built in 1924. Because of problems to work out with developing on sand, Mission Beach developed later than the neighboring communities of Ocean Beach to the south and Pacific Beach to the north. As a result of a new official subdivision in 1914, encouraged by land sales in those next-door communities and a new wooden bridge linking Mission Beach with Ocean Beach, John D. Spreckels offered small lots for sale. As a result, Mission Beach is the most densely developed residential community in San Diego with a land use designation across the majority of its land area of 36 dwelling units per acre. It also has the smallest lots in the city, ranging from 1,250 square feet (116 m) to 2,400 square feet (220 m). Few have been consolidated to form larger lots. Many of the structures within the community have been redeveloped into two-story homes. The wooden bridge to Ocean Beach was closed to traffic in 1950 and demolished in 1951.

Attractions near Mission Beach include SeaWorld in Mission Bay Park and the historic amusement park Belmont Park in South Mission Beach. Belmont Park was originally built as the Mission Beach Amusement Center by John D. Spreckels in 1925 to stimulate real estate sales and to promote his electric railway. Belmont Park now features the original wooden Giant Dipper Roller Coaster as well as newer rides such as the FlowRider at Wave House, Vertical Plunge, Krazy Kars, Tilt-a-Whirl, Liberty Carousel, Crazy Submarine, The Beach Blaster, and The Chaos.

Designed by architect Frank Walter Stevenson, The Mission Beach Plunge in Belmont Park, a 60-foot (18 m)-by-175-foot (53 m) saltwater swimming pool, opened in May 1925 as the Natatorium. The Plunge building enclosing the pool was styled after the Spanish Renaissance architecture of San Diego's Balboa Park structures. The changing rooms appear in the Tom Cruise film Top Gun. Celebrities who once swam at the Plunge include Esther Williams and Johnny Weissmuller. The roof of the building rolled open to make it both an indoor and outdoor pool. The Mission Beach Plunge (now using fresh water) and the Giant Dipper are the only remaining attractions left from Spreckels' original park; the other structures were razed in the late 1980s. The Plunge was saved from demolition after the Save Mission Beach Plunge Committee of residents put a measure to save the pool on the ballot, which was approved unanimously in 1987 by San Diego voters. The Plunge closed in 2014 because of disrepair. Plans to rebuild the Plunge were approved in January 2016. The pool reopened in July 2019.

Also nearby, immediately east of SeaWorld, is an unlined landfill. From 1957 to 1962 large amounts of industrial waste, including millions of gallons of chromic, hydrofluoric, nitric, sulfuric, and hydrochloric acids, dichromate, cyanide, and carbon tetrachloride, were deposited into this landfill. No remediation efforts have occurred.