Bellamy's father, George, was rhythm guitarist in the 1960s pop group The Tornados, who were the first British band to have a United States number one song, with "Telstar". "Knights of Cydonia", a single from Muse's fourth album Black Holes and Revelations, is often cited as a tribute to that song, with its space rock sound and accompanying video depicting a cowboy's quest through a human landscape. Bellamy's mother, Marilyn, was born in Belfast, and moved to England in the 1970s. On her first day in England she met George, who was at the time working as a taxi driver in London. They later moved to Cambridge, where Matthew's older brother Paul was born, followed a couple of years later by Matthew himself. Bellamy started playing the piano at age 6 and guitar when he was 14.
In the mid-1980s, the family moved to Teignmouth, Devon. After the divorce of Bellamy's parents, he moved in with his grandmother, who pushed him towards learning to play the guitar at the age of fourteen.