"Mr. Blue Sky" is a song by English rock group Electric Light Orchestra (ELO), featured on the band's seventh studio album Out of the Blue (1977). Written and produced by frontman Jeff Lynne, the song forms the fourth and final track of the "Concerto for a Rainy Day" suite, on side three of the original double album. "Mr. Blue Sky" was the second single to be taken from Out of the Blue, peaking at number 6 in the UK Singles Chart and number 35 in the United States. The song was played as a wake-up call to astronaut Christopher Ferguson on Day 3 of STS-135, the final mission of Space Shuttle Atlantis.