The IRT Second Avenue Line, also known as the Second Avenue Elevated or Second Avenue El, was an elevated railway in Manhattan, New York City, United States, from 1878 to 1942. It was operated by the Interborough Rapid Transit Company until 1940, when the city took over the IRT. Service north of the 57th Street station ended on June 11, 1940; the rest of the line closed on June 13, 1942.

The Interborough Rapid Transit Company (IRT) was the private operator of New York City's original underground subway line that opened in 1904, as well as earlier elevated railways and additional rapid transit lines in New York City. The IRT was purchased by the city in June 1940, along with the younger BMT and IND systems, to form the modern New York City Subway. The former IRT lines are now the A Division or IRT Division of the Subway.