The Greater Cleveland Regional Transit Authority (officially the GCRTA, but historically and locally referred to as the RTA) is the public transit agency for Cleveland and the surrounding suburbs of Cuyahoga County in Ohio, United States. RTA is the largest transit agency in Ohio, with a ridership of 24,875,000, or about 86,100 per weekday as of the second quarter of 2025.

RTA owns and operates the RTA Rapid Transit rail system (called "The Rapid" by area residents), which consists of one heavy rail line (the Red Line) and three light rail lines (Blue, Green, Waterfront). The bulk of RTA's service consists of buses, including regular routes, express or flyer buses, loop and paratransit buses. In December 2004, RTA adopted a revised master plan, Transit 2025, in which several rail extensions, bus line improvements and transit oriented developments are discussed.

RTA's major predecessor, the Cleveland Transit System, was the first transit system in the western hemisphere to provide direct rapid transit service from a city's downtown to its major airport.

In 2007, RTA was named the best public transit system in North America by the American Public Transportation Association, for "demonstrating achievement in efficiency and effectiveness."

The GCRTA was established on December 30, 1974, and on September 5, 1975 assumed control of the Cleveland Transit System, which operated the heavy rail line from Windermere to Cleveland Hopkins Airport and the local bus systems, and Shaker Heights Rapid Transit (the descendant of a separate streetcar system formed by the Van Sweringen brothers to serve their Shaker Heights development), which operated the two interurban light rail lines from downtown to Shaker Heights. CTS had been formed in 1942, when the city of Cleveland took over the old Cleveland Railway Company. However, with Cleveland's dwindling population over the previous two decades, its revenue dwindled significantly. The problem really manifested itself with a 17-day strike in July 1970. City and county leaders concluded that a regional approach was the only way to save it.

A month after its formation, RTA assumed control over the suburban bus systems operated by Maple Heights, North Olmsted, Brecksville, Garfield Heights and Euclid.

The RTA had to undertake a number of renovations to the rail system, as the Shaker Heights lines (renamed the Blue and Green lines) had not been significantly renovated since their creation in 1920. They were largely rebuilt by 1981 and the downtown station at Cleveland Union Terminal, later renamed Tower City Center, was heavily rebuilt by 1987. In 1994, a walkway and skyway was added from the Tower City station to the Gateway Sports and Entertainment Complex and the Blue and Green lines were extended to the North Coast Harbor area by 1996.

Seventy-five Cleveland Transit System PCC streetcars were sold in 1952 to Toronto to be used by the Toronto Transit Commission (TTC). The last of the Cleveland PCC models operated for 30 years in Toronto, until 1982. Cleveland Transit also sold eight Marmon-Herrington TC44 trolleybuses in 1963 to the TTC.