Theme from The Greatest American Hero (Believe It or Not)

"Theme from The Greatest American Hero (Believe It or Not)" is a song composed by Mike Post with lyrics by Stephen Geyer, and sung by American singer Joey Scarbury. It serves as the theme song for the 1980s television series The Greatest American Hero. The track was later included on Scarbury's 1981 debut album America's Greatest Hero.

In a 2005 interview, composer Mike Post said that Joey Scarbury “was an artist that I was producing, and had produced on three different record companies before that – unsuccessfully in terms of hits, but successfully in terms of how great a singer he was.” Post recalled that producer Stephen J. Cannell told him, “This guy’s flying around in a suit and he lost the instructions, and he’s got this right-wing CIA agent for a control guy.” Post responded, “Cannell, this is nuts.” Post had written a theme song with lyrics by Stephen Geyer for the short-lived Cannell series Richie Brockelman, Private Eye, and Cannell suggested doing that again for this show. Post responded, “Yeah, that’s a good idea. We’ll call up Stephen Geyer and see if he can write a lyric where maybe he can make an analogy between love and flying in a suit.”

The theme song became a popular hit during the run of The Greatest American Hero. "Believe It or Not" entered the top 40 of the Billboard Hot 100 on June 13, 1981, eventually peaking at No. 2 during the weeks ending August 15–22, 1981, kept off the top spot by "Endless Love" by Diana Ross and Lionel Richie, and spending a total of 18 weeks in the top 40. On the Adult Contemporary chart, "Believe It or Not" went to number 3. It also peaked at the number one position on the Record World chart.

In the season 8 episode of Seinfeld titled "The Susie", an answering machine message consists of a parody of "Believe It or Not". As a tribute to the Seinfeld episode, the song appeared in a 2021 TV commercial for Tide that aired during CBS' telecast of Super Bowl LV on February 7, 2021, starring Jason Alexander, whose character George Costanza recorded the parody lyrics as his answering machine message.

In the Homestar Runner Halloween special "The House That Gave Sucky Treats", Homestar Runner dresses as The Greatest American Hero. When greeted, Homestar sings a parody of the America's Greatest Hero theme song.

The song was also used as the opening theme for the Brad Jones comedy-review show, The Cinema Snob.