July 9 Avenue (Spanish: Avenida 9 de Julio) is a major thoroughfare in the city centre of Buenos Aires, Argentina. Its name honors Argentina's Independence Day, July 9, 1816.

The avenue runs around 3 kilometres (1.9 mi) to the west of the Río de la Plata waterfront, from the Retiro district in the north to Constitución station in the south. The avenue has up to seven lanes in each direction and is flanked on either side by parallel streets of two lanes each. Through the centre of the avenue runs one of the city's Metrobus (Bus rapid transit) corridors, which stretches 3 kilometres (1.9 mi) and was inaugurated in July 2013. There are two wide medians between the side streets and the main road. It is currently the widest avenue in the world.

The northern end of the avenue is connected to the Arturo Illia expressway (which connects to Jorge Newbery airport and the Pan-American highway) and to Libertador avenue. The southern end is connected to the 25 de Mayo tollway (serving the west side of Greater Buenos Aires as well as Ezeiza airport) and the 9 de Julio elevated expressway which provides access to the two main southbound roads out of the city (route 1 to La Plata and route 2 to Mar del Plata). The Republic Square is located on the intersection of this Avenue with the Corrientes Avenue and on that point is sited the Obelisk of Buenos Aires.