Commonwealth Avenue (Tagalog: Abenida Komonwelt), formerly known as Don Mariano Marcos Avenue (Tagalog: Abenida Don Mariano Marcos), named after the father of President Ferdinand Marcos, is a 12.4 km (7.7 mi) highway located in Quezon City, Philippines which spans from 6 to 18 lanes and known as the widest in the Philippines. It is one of the major roads in Metro Manila and is designated as part of Radial Road 7 (R-7).
The Commonwealth Avenue starts from the Quezon Memorial Circle inside the Elliptical Road, it passes through the areas of Philcoa, Tandang Sora, Balara, Batasan Hills and ends at Quirino Highway in the Novaliches area.
The Commonwealth Avenue is divided to two portions, the 6-8 lane Fairview Avenue and the 18-lane Don Mariano Marcos Avenue. The Don Mariano Avenue was constructed in the late-1960s as a 2-lane highway to offer a route towards the Batasang Pambansa Complex. Quezon City was then the capital of the Philippines, and embassies were to be put up on the stretch of highway. Because the country's capital was moved back to Manila in 1976, other establishments were put up instead.
The Don Mariano Marcos Avenue was later extended from the Elliptical Road to Calle Espana (now known as Espana Boulevard). The Don Mariano Marcos Avenue was later renamed into two parts, the Commonwealth Avenue and Quezon Avenue. Later Commonwealth Avenue regained the 8-lane Fairview Avenue, which ends in the Jordan Plains Subdivision in Novaliches.
In the 1980s, the road was widened into a 6-lane highway. During the late 1990s and early 2000s (decade), the avenue was prone to heavy traffic and accidents due to the increase in number of public transportation vehicles plying the highway, and sidewalk vendors crowding onto the road. In the late 2000s (decade), the Metropolitan Manila Development Authority cleared the sidewalk vendors, especially in the Tandang Sora area, which was prone to heavy rush hour traffic. Fairview Avenue uses stoplights and center island splittings in its intersections, while the Don Mariano Marcos Avenue uses interchanges in its intersections.