This article deals with the bus company which operated from 1964 until 1993. For the successor agency, see Los Angeles County Metropolitan Transportation Authority.

The Southern California Rapid Transit District (almost always referred to as RTD or rarely as SCRTD), was the successor to the original Metropolitan Transit Authority after it virtually went bankrupt. It was created by an act of the California State Legislature in 1964, and took over all of the bus service operated by MTA on November 5, 1964. RTD was merged into the Los Angeles County Metropolitan Transportation Authority in 1993.