The Los Angeles Metropolitan Transit Authority (sometimes referred to as LAMTA or MTA I) was a public agency formed in 1951. Originally tasked with planning for rapid transit in Los Angeles, California, the agency would come to operate the vestiges of defunct private transit companies in the city.

Formed in 1951,^[1][2] LAMTA's original mandate was to do a feasibility study for a monorail line which would have connected Long Beach with the Panorama City district in the San Fernando Valley via Downtown Los Angeles.

The agency's powers were expanded in 1954, authorizing it to study and propose an extensive regional transit system.^[3] In 1957, another expansion of the agency's powers authorized it to operate transit lines, and it subsequently purchased the bus and streetcar lines then being operated by Metropolitan Coach Lines, which had taken over passenger service of the Pacific Electric Railway in 1953, as well as the bus and streetcar lines of the Los Angeles Transit Lines, successor to the Los Angeles Railway.^[4] Both companies, as well as MCL subsidiary Asbury Rapid Transit System, were acquired for $34 million (equivalent to $387 million in 2023).^[5] The MTA began operating the lines on March 3, 1958,^[6] and continued to do so until the agency was taken over by the Southern California Rapid Transit District on November 5, 1964.^{[7][8][9][10]}

During the MTA's tenure, the last remaining rail transit lines in Los Angeles were abandoned and replaced with bus service, the last former Pacific Electric line in April 1961,^[11][12][13] and the last former Los Angeles Railway lines in 1963.^[14]

• Jim Wilson (Los Angeles), MTA secretary