Mark Williams (born 17 June 1959) is an English actor, comedian, scriptwriter and presenter. He is known as one of the stars of the popular BBC sketch show, The Fast Show as well as for the role of Arthur Weasley in the Harry Potter films.
He is a fan of Aston Villa and Brighton & Hove Albion.
In the Academy Award-winning film Shakespeare in Love, Williams portrayed Wabash, the stuttering actor who recited the Prologue and Epilogue in the production of Romeo and Juliet. More recently he has begun to receive notice for appearing in the second, third, fourth, and fifth Harry Potter films.
On 3 July 2006 he appeared as an old roadie friend of Tommy Saxondale in the third episode of the BBC comedy series Saxondale. He presented a documentary series titled Mark Williams' Big Bangs on the history of explosives, a follow-up to previous series Mark Williams on the Rails, Industrial Revelations and More Industrial Revelations.
He starred in the 1997 film The Borrowers with actors Tom Felton and Jim Broadbent. Later, the three would all be cast to star in the Harry Potter films, with Tom portraying Draco Malfoy and Jim portraying Horace Slughorn. Coincidentally, the main character of The Borrowers is named Ocious P. Potter.