The Sunset District is the largest district within the city of San Francisco, and with a population of over 85,000 it is also the most populous. Golden Gate Park forms the neighborhood's northern border, and the Pacific Ocean (or, more specifically, the long, flat strand of beach known as Ocean Beach) forms its western border. The Sunset District's southern and eastern borders are not as clearly defined, but there is a general consensus that the neighborhood extends no farther south than Sigmund Stern Grove and Sloat Boulevard and no farther east than Stanyan Street (just east of the Parnassus campus of the University of California, San Francisco) and Laguna Honda Hospital. Prior to the residential and commercial development of the Sunset District, much of the area was covered by sand dunes and was originally referred to by 19th century San Franciscans as "the Outside Lands."

The Sunset District and the neighboring Richmond District (on the north side of Golden Gate Park) are often collectively known as The Avenues, because the majority of both neighborhoods are spanned by numbered north-south avenues. When the city was originally laid out, the avenues were numbered from 1st to 49th, and the east-west streets were lettered A to X. In 1909, to reduce confusion for mail carriers, the east-west streets and 1st Avenue and 49th Avenue were renamed. The east-west streets were named in ascending alphabetical order in a southward direction after prominent 19th-century American politicians, military leaders, or explorers; 19th-century Mexican landowners; and Spanish conquistadors. 1st Avenue was renamed Arguello Boulevard, and 49th Avenue was renamed La Playa Street (Spanish for "the beach").

Today, the first numbered avenue is 2nd Avenue, starting one block west of Arguello Boulevard, and the last is 48th Avenue near Ocean Beach. The avenue numbers increase incrementally, with one exception: what would be 13th Avenue is known as Funston Avenue, named after Frederick Funston, a U.S. Army general famous for his exploits during the Spanish-American War and Philippine-American War, and for directing the U.S. Army response to the 1906 Earthquake.

The east-west streets in the Sunset appear for the most part in alphabetical order. These streets are: Lincoln Way(bordering the south side of Golden Gate Park), Hugo (from Arguello to 7th Avenue only), Irving, Judah, Kirkham, Lawton, Moraga, Noriega, Ortega, Pacheco, Quintara, Rivera, Santiago, Taraval, Ulloa, Vicente, Wawona, Yorba, and Sloat Boulevard. "X" was originally proposed to be Xavier, but was changed to Yorba due to a pronunciation controversy.