48 Hours, known for a period of time as 48 Hours Investigates and 48 Hours Mystery, is an American documentary news magazine television show broadcast on CBS. The show has been broadcast on the network since January 19, 1988, in the United States. The show airs Saturdays at 10:00 p.m. Eastern and Pacific Time, as part of the network's placeholder Crimetime Saturday block; as such, it is currently one of only two remaining first-run prime time shows (excluding sports) airing Saturday nights on the major American broadcast television networks (along with Univision's Sabadazo). The show sometimes airs two-hour editions or two consecutive one-hour editions, depending on the subject involved or to serve as counterprogramming against other networks. Judy Tygard was named senior executive producer in January 2019, replacing Susan Zirinsky, who served as executive producer since 1996 until her early 2019 appointment as president of CBS News.

Reruns of 48 Hours are regularly broadcast on Investigation Discovery, the Oprah Winfrey Network and TLC as part of their daytime and/or weekend schedules, with varying titles based on the edition's subject matter (such as 48 Hours Hard Evidence, 48 Hours Investigates (a title that has also been used for the CBS broadcasts), 48 Hours on OWN or 48 Hours on ID).

The program was created by former CBS News president Howard Stringer. It drew its title, inspiration and original format from the CBS News documentary 48 Hours on Crack Street, which aired in September 1986, centering on the drug crisis plaguing a number of U.S. neighborhoods. Like the original documentary, the program originally focused on showing events occurring within a 48-hour time span; this format was eventually phased out by the early 1990s.

One of the contributors to that program, CBS News correspondent Harold Dow, had been a member of the 48 Hours on-air staff since its premiere. Dan Rather, at the time also serving as anchor of the CBS Evening News, was the primary host of 48 Hours for its first 14 years on the air. In 1997, CBS aired a special episode of 48 Hours titled Property of 48 Hours, which focused on some of the stories over the program's first nine years.

After low ratings on Saturday nights, the show was moved to Wednesday nights, replacing the comedies Lenny and Doctor Doctor, and it was soon to be moved to the 10:00 p.m. slot.

In the mid-2000s, the program transitioned into its current format, originally known as 48 Hours Mystery although it has since reverted to its original title, which mainly presents "true crime" documentaries.

In 2009, the program featured interviews with Jodi Arias concerning the murder of her former boyfriend, Travis Alexander. These recordings were later used in 2011 as evidence in court to convict Arias, the first time the program's interviews had ever been used in a death penalty trial.

On September 17, 2011, 48 Hours began broadcasting in high definition, making it the last prime time newsmagazine on American broadcast television to convert to the format.