Matthew Rhys was born on 8 November 1974 in Cardiff, Wales, the son of headmaster Glyn Evans and teacher Helen Evans. He grew up in a Welsh-speaking household and was educated at two Welsh-medium schools, Ysgol Gynradd Gymraeg Melin Gruffydd in Whitchurch and Ysgol Gyfun Gymraeg Glantaf in Llandaff North, before training at the Royal Academy of Dramatic Art (RADA) in London, from which he graduated in 1996.
Rhys began his professional career on stage, appearing in the 1997 production of Cardiff East and later in the West End revival of The Graduate. His early screen work included the film Titus (1999), the Welsh comedy-drama Very Annie Mary (2001), directed by fellow Welsh filmmaker Sara Sugarman, and the television series The Lost World. In 2003 he appeared in the ITV wartime drama mini-series P.O.W.
His profile grew internationally with the role of Kevin Walker in the American family drama Brothers & Sisters (2006–2011), followed by his acclaimed performance as Soviet spy Philip Jennings in the espionage drama The Americans (2013–2018), for which he won the Primetime Emmy Award for Outstanding Lead Actor in a Drama Series in 2018. He went on to play the title role in the HBO period drama Perry Mason from 2020, earning a Golden Globe nomination, and had earlier portrayed fellow Welshman Dylan Thomas in the 2008 film The Edge of Love. His film credits also include The Post (2017) and A Beautiful Day in the Neighborhood (2019).
Although based for long periods in the United States, Rhys has spoken often of his deep attachment to Cardiff and Wales, and he shares a long friendship with fellow Welsh actor Ioan Gruffudd. He is in a long-term relationship with actress Keri Russell, with whom he has a son, born in 2016.