The Moody Blues were an English rock band formed in Birmingham in May 1964. The band initially consisted of drummer Graeme Edge, guitarist/vocalist Denny Laine, keyboardist/vocalist Mike Pinder, multi-instrumentalist/vocalist Ray Thomas, and bassist/vocalist Clint Warwick. Originally part of the British beat and R&B scene of the early–mid 1960s, the band came to prominence with the UK No. 1 and US Top 10 single "Go Now" in late 1964/early 1965. Laine and Warwick left the band by the end of 1966, being replaced by guitarist/vocalist Justin Hayward and bassist/vocalist John Lodge. They embraced the psychedelic rock movement of the late 1960s, with their second album, 1967's Days of Future Passed, being a fusion of rock with classical music (performed with the London Festival Orchestra) that established the band as pioneers in the development of art rock and progressive rock. It has been described as a "landmark" and "one of the first successful concept albums".

The group released six more albums and toured extensively until they went on hiatus in 1974. Their records from this period were among the most successful in the progressive rock genre, and produced FM radio hits such as "Nights in White Satin" (1967; charting again in 1972), "Tuesday Afternoon" (1968), "Question" (1970), "The Story in Your Eyes" (1971), "Isn't Life Strange" (1972), and "I'm Just a Singer (In a Rock and Roll Band)" (1973). After resuming activities in 1977, Pinder left the following year and was replaced by former Yes keyboardist Patrick Moraz. In the 1980s they took on a more synth-pop sound, having hits with "Gemini Dream" (1981), "The Voice" (1981), "Your Wildest Dreams" (1986) and "I Know You're Out There Somewhere" (1988). "Your Wildest Dreams" made the Moody Blues the first act to earn each of its first three Top 10 singles in the United States in three different decades. Moraz departed in 1991, followed by Thomas in 2002. The band's last studio album was the Christmas album December (2003), after which they decided against recording any further studio albums. They continued to tour throughout the 2000s and later reunited periodically for events, one-off concerts, short tours and cruises, until Graeme Edge, the last remaining original member, retired in 2018.

Clint Warwick died in 2004, followed by Ray Thomas in 2018, Graeme Edge in 2021, Denny Laine in 2023, and Mike Pinder in 2024. Justin Hayward, John Lodge and Patrick Moraz all remain active in music.

The Moody Blues have sold 70 million albums worldwide, including 18 platinum and gold LPs. They produced 16 studio albums, six of which made the US Top 20 (with two reaching No. 1) and eight of which made the UK Top 20 (with three reaching No. 1). They were inducted into the Rock and Roll Hall of Fame in 2018, for "over 50 years of exhilarating and significant music that has influenced countless musicians and rocked fans around the world".