Ifans was born Rhys Evans in Haverfordwest, Pembrokeshire, Wales to Beti-Wyn, a nursery school teacher, and Eirwyn Evans, a primary school teacher. He has adopted the Welsh spelling of his surname. Ifans grew up in Ruthin, in North Wales, and attended Ysgol Maes Garmon, a Welsh language secondary school in Mold, Flintshire, where he sat his O levels and A levels. He also attended youth acting schools at Theatr Clwyd, Mold. His first language is Welsh and he says that he began using the Welsh spelling of his surname, "just to be difficult". His brother, Ll?r Evans, is also an actor. They starred together in the Welsh produced film, Twin Town. As of late 2007, he is said to be dating British actress, Sienna Miller, getting a swallow tattoo on his left wrist to match hers.

In 1990 Ifans presented Sdwnsh (Welsh for "Mash"), an anarchic children's quiz. In total 31 fifteen minute programmes were broadcast on S4C.

Ifans appeared in many Welsh language television programmes before embarking on his film career, as well as performing at the Royal National Theatre, London and the Royal Exchange Theatre, Manchester.

He was briefly lead vocalist of the rock band Super Furry Animals before they found national success.

His film roles include: Eyeball Paul in Kevin and Perry Go Large (2000), Nigel in The Replacements (2000), Iki in The 51st State (2001), William Dobbin in Vanity Fair (2004) and Vladis Grutas in Hannibal Rising (film) (2007). He also played Jed Parry in the film version of Ian McEwan's Enduring Love (film) and the lead role in Danny Deckchair (2003) as Danny Morgan.

In 2005, Ifans picked up a BAFTA for his critically acclaimed portrayal of iconic comedian Peter Cook in the TV film Not Only But Always. Later that year he made a guest appearance for the rock band Oasis in the video for their single "The Importance of Being Idle" for which he accepted their award for Video Of the Year at the 2005/2006 NME Awards. This was not Ifans' first foray into the world of music videos, he has also made appearances in the music videos for "God! Show Me Magic" by the Super Furry Animals, "Mulder & Scully" by Catatonia and "Mama Told Me Not To Come" by Tom Jones and the Stereophonics.

He is known to American viewers as "Adrian", the pompous, arrogant, eldest brother from Little Nicky, as well as his "breakout" role as Spike in British film Notting Hill (1999).

In December 2006 he returned to the London stage for the first time since 2003 in Michael Grandage's production 'Don Juan In Soho' at the Donmar Warehouse (run ended 10th February 2007). He had appeared previously at the Donmar in 2003's 'Accidental Death Of An Anarchist'. Earlier stage work includes 'Hamlet' at Theatre Clwyd, 'A Midsummer Night's Dream' at the Regent's Park Theatre and 'Under Milk Wood' and 'Volpone' at the Royal National Theatre.

On 16th July 2007 he received an Honorary Fellowship from Bangor University in North Wales, for services to the film industry. In 2002 he gained some controversy in the British media for his alleged support of Welsh nationalist group Meibion Glyndwr, a militant group who support violence against English home owners in the Welsh heartlands. This was due mainly to some comments he made in an interview conducted by Mariella Frostrup for The Observer newspaper.

--Wikipedia