Sants-Montjuïc (Catalan pronunciation: [ˈsanz muɲʒuˈik]) is one of the ten districts Barcelona has been split in since 1984, numbered District 3. Comprising very different areas of the city, it covers the southern part of Barcelona, joining the two former districts II (made up by Montjuïc and Poble-Sec) and VII (Sants - Hostafrancs - La Bordeta), as well as the different areas comprised in the Zona Franca. As of the 2005 census, it had a population of 177.636. It borders Les Corts, Eixample, Ciutat Vella, and the municipalities L'Hospitalet de Llobregat and El Prat de Llobregat.
It was one of the former municipalities added to Barcelona. The former municipality had the main nucleus in the neighbourhood of Sants but other current neighbourhoods of the district belonged to that municipality.