Avenida Presidente Julio Argentino Roca (also known as Diagonal Sur), is a main artery in the Monserrat quarter of Buenos Aires, Argentina. It is oriented north-east/south-west, diagonally bisecting the city blocks (manzanas) which give the city centre a checkerboard plan. It is named after President Julio Argentino Roca, who held power from 1880 to 1886, and from 1896 to 1904.
The north-west corner of Plaza de Mayo is the start of Avenida Presidente Julio Argentino Roca (i.e. the corner of Hipolito Yrigoyen and Bolivar street), just to the north of the Legislatura. At the junction with Peru street is located equestrian monument to Julio Argentino Roca.
Below the entire length of the avenue runs Line of the Buenos Aires Metro, which has two stations along the Diagonal (stations Bolívar and Belgrano).