William Leonard Pereira (April 25, 1909 – November 13, 1985) was an American architect from Chicago, Illinois, who was noted for his futuristic designs of landmark buildings such as the Transamerica Pyramid in San Francisco.

He worked out of Los Angeles and was known for his love of science fiction and expensive cars, but mostly for his style of architecture, which helped define the look of mid-20th century America.

With his brother, Hal Pereira, he designed the Esquire Theater at 58 East Oak Street, considered one of Chicago's best examples of Art Deco style.

He had two wives, former model and actress Margaret McConnell (1910–2011, married June 24, 1934) and Bronya Galef; the latter marriage ending with his death.

A pioneer in the design of heat-efficient buildings, he often employed concrete façade systems that shaded the windows, which were typically of bronze reflective glass, from direct sunlight.

[citation needed] According to Pereira's daughter, Monica, one of his favorite buildings of his own was the complex[7] he designed for the Municipal Water District in Los Angeles in 1963.

He is also responsible for creating the monumental Spanish-inspired facades that defined Robinson's department stores for nearly 20 years, and he was the architect of Pepperdine University at Malibu, named by the Princeton Review as the most beautiful college campus in America.

[10] Perhaps his greatest lasting legacy besides his buildings are the numerous respected architects who came out of both Pereira's firm and the classes he taught at USC, including Gin Wong and Frank Gehry.