Davies was born in Loughton, Essex. His childhood years were spent in Chingford. When Davies was six, his mother died from leukaemia and he was raised by his father.
Davies attended Staples Road School in Loughton and was privately educated at the independent Bancroft's School in Woodford Green, where he gained eight O-Levels. He then moved on to Loughton College of Further Education where he gained four more O-Levels and two A-Levels (Communications & Theatre Studies). He graduated in Drama & Theatre Studies from the University of Kent in 1988, and was awarded an Honorary Doctorate by the university in 2003.
Davies began performing stand-up comedy in 1988 at the Whitstable Labour Club. In 1991, he was named Time Out's Best Young Comic. He continued touring and performing in the UK and Australia, winning the Edinburgh Festival Critics Award for Comedy in 1994. That show was released on video and audio cassette in 1995 as Alan Davies Live at the Lyric recorded at the Lyric Theatre as part of the Perrier Pick of the Fringe season in October 1994.
A version of his show 'Urban Trauma', which ran in the West End at the Duchess Theatre and toured the UK and Australia, was shown on BBC One in 1998.
In 2012, Davies planned a new tour called "Life is Pain". The title for this show came from a story he heard about a six-year-old girl being told off by her mother and responding "Life is pain". Davies said "This really made me laugh". The tour was broadcast on Dave.
In 1994 and 1995, Davies hosted Alan's Big One for three series on Radio 1 before appearing in Channel 4's spoof travel show One for the Road (made by Channel X in 1994/5). He later played the title role in Jonathan Creek, as a trick-deviser for a stage magician with a side interest in solving crimes, between 1997 and 2004. Jonathan Creek won a BAFTA for Best Drama and was the show which brought Davies to mainstream attention.
On New Year's Day 2009, a special episode of Jonathan Creek, "The Grinning Man", was broadcast on the BBC. Davies returned to Creek at Easter 2010 for a one-off episode, "The Judas Tree". However, the programme did return in Easter 2013 for the episode of "The Clue of the Savant's Thumb". Davies has confirmed in an interview that there will be at least three further specials.
Davies co-wrote and starred in his own radio sitcom, The Alan Davies Show, in 1998. Cassettes of the show were produced and released by the BBC, with episodes broadcast on the digital radio station BBC7. He played Russell Boyd in the BBC comedy A Many Splintered Thing, also in 1998 and 2000.
In 2001 Davies played Robert Gossage in Bob and Rose, a comedy drama about a gay man falling for a woman. He won the Best Actor award at the Monte Carlo TV Festival for his performance. He also played Jack the dog in the radio sitcom About a Dog. In 2003, Davies appeared as a Star in a Reasonably-Priced Car on Top Gear with a time of 1:54 in wet conditions. He returned in Series 8 with 1:50.3 in dry conditions. During a period from the mid-1990s to 2002, Davies advertised for Abbey National.
Davies took on a less comedic role in 2004, starring as Henry Farmer, a maverick barrister, in ITV Sunday night drama The Brief, for two series. Subsequent drama roles include Superintendent Mallard in Agatha Christie's Marple (ITV, 2008), as well as appearances in The Good Housekeeping Guide (BBC One, 2006), Roman Road (ITV 2004) and Hotel Babylon (BBC One, 2008).
He argued the case for John Lennon as the greatest Briton of all time on the BBC's Great Britons series in 2002. In 2007, Davies starred in the second episode of ITV's You Don't Know You're Born and on The Unbelievable Truth.
He has appeared in an episode of the BBC science programme Horizon in which Professor Marcus du Sautoy attempted to introduce him to elements of mathematical thought which was broadcast on BBC Two on 31 March 2009. He went on to appear in Horizon for a second time in November 2009, this time leading the episode — du Sautoy also returned as a guest speaker.
On 16 May 2010, Davies appeared in "Your Sudden Death Question", an episode of the ITV detective series Lewis, as Marcus Richard, a scamming quizmaster at a competition held in an Oxford college, at which some of the contestants are murdered. In September 2010, he began a three-part documentary series Alan Davies' Teenage Revolution (Channel 4), partly based on his autobiographical book My Favourite People and Me, 1978-88.
In September 2010, a BBC comedy series entitled Whites starring Davies as a chef premiered. It was however cancelled after this first series. It is believed to have been a victim of the cuts at the BBC subsequent to the reduced licence fee settlement.
In April 2011, Davies appeared as the guest on the return of the ABC TV conversation program A Quiet Word With .... In 2011 Davies was also one of the judges on the ITV programme Show Me The Funny, a talent contest for new and aspiring stand-up comedy performers.
In September 2012, Davies made his first appearance on Channel 4's Big Fat Quiz series, winning The Big Fat Quiz of the '90s alongside Phill Jupitus.
In February 2014, Davies presented a chat show Alan Davies Après-Ski on BBC Two, which looked at some of the highlights of the 2014 Winter Olympic Games. He also co-hosted the Brazilian Banter podcast for ITV with Tom & Dom from Bantams Banter. The show was a satirical look at the 2014 FIFA World Cup hosted by Brazil.
Since 2014, he has hosted The Dog Rescuers for Channel 5 and chat show Alan Davies: As Yet Untitled for Dave.
He has been approached by Disney to provide the voice of Bob Godfrey for an animated biopic on the life of the celebrated animator.
Davies currently appears as the permanent panellist on the BBC Two quiz game QI, which was hosted by Stephen Fry from 2003 to 2015 but since his departure is now hosted by Sandi Toksvig. He also contributed "four words" to the QI book The Book of General Ignorance (which appear after Stephen Fry's foreword), "Will this do, Stephen?". Davies has appeared on almost every regular episode of the show, though in one episode (Episode 10 of Series D, "Divination") he appeared in only the first few minutes, in a pre-recorded scene, as he was in Paris attending the 2006 Champions League final during the actual recording. His chair was empty for the rest of the episode although his voice was heard during "General Ignorance". He also did not appear in the 2011 Comic Relief episode.
Davies married writer Katie Maskell on 13 January 2007 after a 6-month engagement. The couple first met backstage at QI in 2005. Friend and comedy partner Bill Bailey was Davies's best man and delivered a speech at the ceremony. They have three children.
Davies has narrated an anti-vivisection video called Wasted Lives.
In late 2007 The Times and Daily Telegraph reported that Davies bit the ear of a homeless man. Davies had just left a wake at the nearby Groucho Club. He told The Times in 2009, "He wasn't a tramp. He was a raging, horrendous arsehole. He called me a cunt several times. Or if it wasn't him, it was his mate. And, yes, I went for him and, yes, I did it in what turned out to be an amusing way." Following the incident, Davies was banned from the Groucho Club.
Davies is a lifelong fan and season ticket holder of Arsenal FC. Davies also used to host the podcast "It's Up For Grabs Now" which took a light-hearted look at goings on at the club. He is also a vegetarian. On 18 January 2011, he began hosting the new Arsenal Podcast "The Tuesday Club" with Ian Stone, Keith Dover, Tayo Popoola and Skint Records founder Damian Harris.
He is a supporter of the Labour Party. Davies said: “Social injustice is important to me,” “Life isn’t about every man for himself. Life should be about co-operation and collaboration.”
Davies's first book, the autobiographical My Favourite People and Me, 1978-88 was published by Michael Joseph (Penguin Books) in September 2009. Of the memoir, Davies said he wished to "attempt to remember what I liked as a boy/youth/idiot and to work out why". The titular favourite people include Anton Chekhov, John Belushi, Barry Sheene, Margaret Thatcher ("only for a few days" the author allows), John McEnroe and Starsky and Hutch. The book also mentions Arsenal F.C., the football team supported by Davies; he recalls as a child his mother sewing their club badge and captain's number onto his shirt, done only a year or so before she died. The paperback was published under the title Rebel Without A Clue: How the 80s Made Me.Urban Trauma (1998)
Life is Pain: Live in London (18 November 2013)
Little Victories (28 November 2016)