Tram route 81 in Brussels, Belgium is a tram route in the south of the city who connects the stop Marius Renard in the municipality of Anderlecht with the multimodal stop Montgomery station in Woluwe-Saint-Pierre. The route also crosses the municipalities of Saint-Gilles, Ixelles, the City of Brussels and Etterbeek. It has connections with metro stations in Saint-Guidon metro station, Brussels-South railway station (which also connects with the train), Merode station (which is also a train station) and Montgomery station. The route also crosses the major tram routes 3 and 4 at Horta.
The route was changed in the 2000s, with the former section between the Brussels-South railway station and the Heysel metro station being replaced by a section between the Brussels-South railway station and Marius Renard. The former route entered the North-South underground section right after Brussels-South at Lemonnier.