The Mass Ave Cultural Arts District, colloquially known as Mass Ave, is one of seven designated cultural districts in Indianapolis, Indiana, United States. The district centers on 0.86 miles (1.38 km) of its namesake Massachusetts Avenue, from its southern terminus at New York and Delaware streets to its northern terminus at Bellefontaine Street. The avenue is one of the four original diagonal streets included in Alexander Ralston's plan of 1821. Mass Ave also contains the Massachusetts Avenue Commercial District, a historic district included on the National Register of Historic Places since 1982.

Today it lies at the heart of the city's arts district. It offers some of the city's most visible theaters and art galleries as well as a number of shops and eateries.^[1]

Gentrification in the 1990s propelled the area from squalor to one of the city's more fashionable addresses. Currently, redevelopment of Mass Ave focuses on fostering locally owned shops, theaters, and restaurants.^[2]

• Athenæum (Das Deutsche Haus): building houses Young Actors Theatre and the Rathskeller Restaurant, the city's oldest restaurant still in operation.
• Old National Centre: is the headquarters of the Indianapolis Ancient Arabic Order of the Nobles of the Mystic Shrine.^[3]