Rhys Ifans was born Rhys Owain Evans on 22 July 1967 in Haverfordwest, Pembrokeshire, the son of primary school teacher Eirwyn Evans and nursery school teacher Beti-Wyn Evans. He grew up in Ruthin, Denbighshire, in North Wales, where he was raised speaking Welsh as his first language and attended primary school at Ysgol Pentrecelyn.
He was educated at Ysgol Maes Garmon, a Welsh-medium secondary school in Mold, and took acting classes at the Theatr Clwyd youth theatre before training at the Guildhall School of Music and Drama in London. Early in his career he presented Welsh-language television programmes for S4C, and changed his professional surname from Evans to the Welsh spelling Ifans.
Ifans made his breakthrough in the Welsh cult film Twin Town (1997), starring alongside his real-life younger brother, Llyr Ifans. International recognition followed with roles including the eccentric Spike in Notting Hill (1999), and he went on to build a long and varied career spanning Kevin & Perry Go Large (2000), Enduring Love (2004) and The Boat That Rocked (2009), as well as playing Xenophilius Lovegood in Harry Potter and the Deathly Hallows - Part 1 (2010) and Dr Curt Connors, also known as the Lizard, in The Amazing Spider-Man (2012) and Spider-Man: No Way Home (2021).
More recently Ifans has taken on major television roles, including Otto Hightower in HBO's House of the Dragon and Mycroft Holmes in the CBS series Elementary, and played the Russian mystic Grigori Rasputin in The King's Man (2021). He remains closely associated with Welsh culture and has performed as a singer with the band The Peth alongside his acting career.