Arthur Stuart is a character of Todd Haynes' Velvet Goldmine movie. He's played by Christian Bale.
Arthur is a journalist who dives into glam rock history (fictional history, that is) to write an article about "Whatever happened to Brian Slade?" He sets out to find the former-rockstar (played by Jonathan Rhys-Meyers), but finds absolutely nothing after the staged death of the Brian.
Interviewing Brian's ex-wife, Mandy Slade (played by a vibrant Toni Collette) and old managers, Arthur starts to reconstruct the life, romances and wickedness of Slade.
Also, as a former glam rock fan, Arthur starts to remember his own teenage life and the discovery of life's excitements through the excess and freedom preached by glam rockers. He remember life with friends from the fictional band The Flaming Creatures: Malcolm (played by Brian Molko), Billy (played by Steve Hewitt), Ray (played by Antony Langdon and Pearl (played by Xavior).
He finally finds out what became of Brian and also gets in touch with his young self. Arthur is the common-person element of the movie, the one character we can all identify with.
Some people write Stuart's name as 'Stewart', but IMDB settles the matter with 'Stuart'.