Mulholland Dam, Gravity dam in Hollywood Hills, United States.

Mulholland Dam is a curved concrete gravity dam in the Hollywood Hills, holding back the Hollywood Reservoir. Its pale grey downstream face is smooth and slightly battered, with faint vertical construction joints. A continuous row of small vertical posts carrying a thin rail runs along the crest, and near the left end a taller rectangular concrete block rises above the parapet line.

Construction of the dam began in August 1923 and was completed in December 1924, the first curved concrete gravity dam built by the Bureau of Water Works and Supply. It was renamed for William Mulholland, the bureau's chief engineer. After the St. Francis Dam failed in March 1928, killing an estimated 430 people, Mulholland ordered the Hollywood Reservoir drawn down, and in 1933–1934 some 330,000 cubic yards of earth were placed on the downstream face.

The dam carries the name of William Mulholland, general manager and chief engineer of the Bureau of Water Works and Supply, who oversaw the Los Angeles Aqueduct and much of the city's water system. The reservoir it holds was first called Weid Canyon, after Danish immigrant Ivar Weid, who lived in the canyon and sold land there in the 1880s; Ivar Avenue in Hollywood also bears his name.

The structure sits in the hills north of Hollywood and can be seen from several viewpoints in the area, accessible via public roads. Visitors should wear sturdy shoes, as paths can be steep and uneven.

After the St. Francis Dam collapse in 1928, authorities decided never to fill the basin completely again to increase safety. Since then, the water level has been intentionally kept below the originally planned height, even though the wall itself remains unchanged.