Mackenzie Crook is an English actor and comedian, best known for playing Gareth Keenan in The Office and Ragetti in the Pirates of the Caribbean films.

Crook was born in Maidstone, Kent, England, and grew up in Dartford. His father, Michael Crook, worked for British Airways and his mother, Sheila, was a hospital manager. When he was ten years old, he was put on a course of hormone therapy for a year due to a growth hormone deficiency. He went to Wilmington Grammar School for Boys, and did his first plays there.

He joined the Orchard Youth Theatre in Dartford when he was about fifteen-years-old and gained his inspiration for acting. During summers he spent time with his uncle in Zimbabwe where he developed a love for painting and grew with an ambition to be a graphic artist. He also greatly admired Kurt Cobain grew his hair long and pursued starting a heavy metal band, but dropped it after deciding his voice wasn't suited for it. Even as a teenager he was still small for his age due to his growth hormone deficiency.

When he was eighteen he applied to the Kent Institute of Art & Design three times but failed to secure a place on each attempt. He spent a while doing part time jobs in a hospital, a chicken factory, a Chimney Sweep, Halfords and Pizza Hut before he turned to writing comedy sketches.

His first short film was called The Man who Fell in Love with a Traffic Cone! There is very little information on the film. Crook began his career as a standup comedian alongside Iain Lee for about eight years, in the guise of Charlie Cheese, "the cheeky chirpy chappy from Chorley". They appeared at the Edinburgh Fringe Festival in the mid-90's as Chalk and Cheese. He had also often performed as a grotesque schoolteacher called Mr. Bagshaw, who is said to be based on a variety of obnoxious teachers he was tutored by while in school. Crook's first major television role was as a comedy sketch contributor on Channel 4's The Eleven O'Clock Show in 1998. He was later a member of the main cast of the BBC sketch show TV to Go in 2001. From 2001 to 2003 he played the role of Gareth Keenan in the popular mockumentary The Office, the role earned him two nominations.

He appeared in Pirates of the Caribbean: The Curse of the Black Pearl (2003), Pirates of the Caribbean: Dead Man's Chest (2006), and in Pirates of the Caribbean: At Worlds End (2007), as Ragetti, a pirate with a comically ill-fitting wooden eye. He has appeared in ads for Visa and M&Ms (as his Ragetti character in both).

He also appeared as Launcelot Gobbo in Michael Radford's 2004 film adaptation of William Shakespeare's The Merchant of Venice. Crook played a minor role in the 2004 film Finding Neverland as a theatre usher. Other films he starred in include The Gathering (2002), Sex Lives of the Potato Men (2004), Churchill: The Hollywood Years (2004), and The Brothers Grimm (2005).

Crook has starred in three of Tim Plester and Ben Gregor's short films: as Gary Tibbs in Ant Muzak (2002), as Servalan in Blake's Junction 7 (2004), and as Glorious George in World of Wrestling (2006). He has also voiced in a television series called Modern Toss and has featured in I Want Candy (2007 film) as Mr Dulberg, a quirky University Professor. He has also performed a duet with Ricky Gervaisin the Concert for Diana.

He also voiced a main character called Rolli in an animated film from Finland called Quest For A Heart Mackenzie will feature in Wyndham Price's drama Abraham's Point as Comet Snape and appear in City of Ember as Looper, and will also be featured in the upcoming documentary Tattoos: A Scarred History (2008). On TV, he is due to appear in an upcoming ITV drama "The Last Van Helsing" as a vampire named Gladiolus Thrip.

He plays the leading role of Paul Callow in the British comedy Three and Out released on April 25, 2008.