West Philadelphia is a section of the City of Philadelphia, Pennsylvania, United States. Though there is no set official definition on the boundaries of the region, West Philly can be described as being from the western side of the Schuylkill River to the city line, with the SEPTA R3 Media-Elwyn line being used as a reference for the southern border. Occasionally West Philadelphia is described as being the area west of the Schuylkill River; this definition would also include Southwest Philadelphia and its neighborhoods.

West Philadelphia's population expanded significantly in the late 1800s and early 1900s and the area was home to a large segment of Philadelphia's middle-class population commuting into the Central Business District a few miles to the East. The Western portion of the neighborhood was once home to some of the most expensive real estate in the country, but over the last 50 years has declined in prominence as crime rates have increased and much of the city's middle and upper classes have migrated to the suburbs and other sections of the city. Striking Victorian architecture remains, recalling the area's glorious past. In recent years, parts of West Philadelphia have undergone "Penntrification," a term that reflects the University of Pennsylvania's role in gentrification of the neighborhood. The area has experienced a resurgence in popularity with young professionals and families.

West Philadelphia is the home to several universities, including the University of Pennsylvania, St. Joseph's University, Drexel University, and the University of the Sciences in Philadelphia.

To people outside of Philadelphia, West Philadelphia is widely known from being mentioned in the theme song to the television series The Fresh Prince of Bel-Air in which Will Smith sings the lyric "In West Philadelphia, born and raised", reflecting his origins in the Wynnefield neighborhood.

West Philadelphia is also the neighborhood of the Pryor family in the NBC drama American Dreams, which is set in the mid-1960's.