Adam Charles Clayton is an English-born Irish musician who is the bass guitarist of the rock band U2. He has resided in County Dublin, Ireland since his family moved to Malahide in 1965, when he was five years old. Clayton attended Mount Temple Comprehensive School, where he met schoolmates with whom he co-founded U2 in 1976. A member of the band since its inception, he has recorded 15 studio albums with U2.

Adam Charles Clayton, the oldest child of Brian and Jo Clayton, was born on 13 March 1960 in Chinnor, Oxfordshire, England. His father was a pilot with the Royal Air Force who moved into civil aviation, and his mother was a former airline stewardess. When Clayton was four years old, his father worked in Kenya as a pilot with East African Airways, with the family residing in Nairobi; Clayton regards this as the happiest period of his childhood. In 1965, the family moved to Malahide, northern County Dublin, Ireland, where Clayton's brother Sebastian was born. The Clayton family became friends with the Evans family (including their son David Evans ("The Edge"), who later co-founded the band U2 with Clayton).

When he was eight years old, Clayton was sent to the private junior boarding Castle Park School in Dalkey, southern County Dublin. Not being sports-oriented, Clayton did not enjoy the school or respond well to its ethos; he found it difficult to settle socially there. He was interested in pop music, which students were not allowed to listen to. He joined the School's "Gramphone Society", which met to listen to classical music. He also took piano lessons for a short time. His introduction to the world of popular music was around age 10, listening to rock operas such as Jesus Christ Superstar and Hair, and other material that was midway between classical and popular music.

When Adam was five years old, he and his family moved to Malahide near Dublin. He started playing guitar when he went to school. He joined the other members of the future U2 band in the same time. Their band was first named "Feedback" and then they changed its name to "The Hype". However, they released their second album on 1981 under the name of U2.

All other U2 members were married by 2006, and Adam was the only member who was still single. In 2006, it was announced that Adam was going to marry Suzanne "Susie" Smith; they dated for almost 10 years before this news was announced. They were planning to marry in the summer of 2007, but they split up in February 2007.

In January 2011, Adam revealed that he was the father of a baby boy, born in 2010. On September 4, 2013, Adam married Mariana Teixeira de Carvalho, in a wedding in Dublin. She is a fashion model from Brazil.

In 2011, Clayton became an ambassador for the Dublin-based St Patrick's Hospital's Mental Health Service "Walk in My Shoes" facility.