"What a Fool Believes" is a song written by Michael McDonald and Kenny Loggins. The best-known version was recorded by the Doobie Brothers for their 1978 album Minute by Minute. Debuting at number 73 on January 20, 1979, the single reached number one on the Billboard Hot 100 on April 14, 1979, for one week. The song received Grammy Awards in 1980 for both Song of the Year and Record of the Year. In 2024, the song was inducted into the Grammy Hall of Fame.

Michael H. McDonald is an American singer, keyboardist and songwriter known for his distinctive, soulful voice and as a member of Steely Dan (1973–1974), and the Doobie Brothers. McDonald wrote and sang several hit singles with the Doobie Brothers, including "What a Fool Believes", "Minute by Minute", and "Takin' It to the Streets." McDonald has also performed as a prominent backing vocalist on numerous recordings by artists including Steely Dan, Christopher Cross, and Kenny Loggins.