Line 9 of the Madrid Metro is a rapid transit line in Madrid that originally opened on 31 January 1980 between Sainz de Baranda and Pavones. Later it was extended from Avenida de América to Herrera Oria on 3 June 1983, though this section was at the time separate from the original part until the missing fragment from Avenida de América to Sainz de Baranda was opened on 24 February 1986.

The Madrid Metro is a rapid transit system serving the city of Madrid, capital of Spain. The system is the 14th longest rapid transit system in the world, with a total length of 293 km (182 mi). Its growth between 1995 and 2007 put it among the fastest-growing networks in the world at the time. However, the European debt crisis greatly slowed expansion plans, with many projects being postponed and canceled. Unlike normal Spanish road and rail traffic, which drive on the right, Madrid Metro trains use left-hand running on all lines because traffic in Madrid drove on the left until 1924, five years after the system started operating.