Guiding Light (known as The Guiding Light before 1975) is an American radio and television soap opera. Guiding Light aired on CBS for 57 years between June 30, 1952, and September 18, 2009, overlapping a 19-year broadcast on radio between January 25, 1937, and June 29, 1956. With 72 years of radio and television runs, Guiding Light is the longest-running American soap opera, ahead of General Hospital.

When the show debuted on radio in 1937, it centered on Reverend John Ruthledge and people whose lives revolved around him. The "Guiding Light" in the show's title originally referred to the lamp in Ruthledge's study that people used as a sign for them to find his help when needed. When the show transitioned to television in the 1950s, the Bauers, a German immigrant family first introduced in 1948, became the focus of the program. Other core families were introduced over the show's run, including the Norrises in the 1960s; the Marlers and the Spauldings in the 1970s; and the Coopers, the Lewises, and the Reardons in the 1980s.

Guiding Light was created by Irna Phillips and Emmons Carlson and began as an NBC Radio serial on January 25, 1937. On June 2, 1947, the series was transferred to CBS Radio, before starting on June 30, 1952, on CBS Television. It continued to be broadcast on radio until June 29, 1956. The series was expanded from 15 minutes to a half-hour during 1968 (and also switched from broadcasting live to pre-taping around this same time), and then to a full hour on November 7, 1977. The series broadcast its 15,000th CBS television episode on September 6, 2006.

On April 1, 2009, CBS announced that it was canceling Guiding Light after 72 years on the air (15 on radio and 57 on television) due to low ratings. The show taped its final scenes on August 11, 2009, and its final episode on the network aired on September 18, 2009. Reruns of The Price Is Right took over the Guiding Light time slot between September 21 and October 2, 2009, for two weeks. On October 5, 2009, CBS replaced Guiding Light with an hour-long revival of Let's Make a Deal, hosted by Wayne Brady.