Through the Keyhole is a British comedy panel game show created by the television producer Kevin Sim and originally presented by Sir David Frost in the studio and Loyd Grossman on location. The location presenter explores celebrities' houses and a panel of other celebrities in the studio try to guess who the famous homeowner is.

The show was originally produced by Yorkshire Television and was broadcast on ITV from 3 April 1987 to 1 May 1995, then on Sky One from 22 February to 23 December 1996 before moving to BBC One from 5 May 1998 to 2 August 2004 and its sister channel BBC Two from 27 February 2006 to 4 June 2008.

In 2013, the show was revived for ITV with Leigh Francis as the host. In February 2020, it was reported that the programme had been cancelled after six series.

Through the Keyhole originally started as a segment on TV-am, first being broadcast on its launch day on 1 February 1983. The idea was created by Kevin Sim as a chance to look around some of the most influential homes with Grossman at the helm as the tour presenter. Grossman was mistakenly given the job after someone had confused him with another journalist. It became a regular feature of TV-am throughout 1983 until May 1985.

In Spring 1986 Frost transferred the concept to Yorkshire Television who picked up the format, to produce a full half-hour programme for ITV, where a celebrity panel tries to guess whose house is being looked at. From 1987 it ran in primetime on Friday nights for eight years on ITV and was rarely out of the top ten entertainment programmes on television. The executive producers were Kevin Sim and Chantal Rickards. From 1996, it was produced by Frost's own production company, Paradine Productions, at Yorkshire Television. That same year, the show also moved to Sky One for one series. It then moved to BBC One Daytime in 1998 until 2004. The final three series aired on BBC Two from 2006 to 2008, after which it was cancelled by the BBC. However, a special aired in March 2011 for Red Nose Day 2011 as part of marathon panel show 24 Hour Panel People.^{[citation needed]}

In 2013, the programme returned on its original broadcast channel ITV with Leigh Francis (in character as Keith Lemon) taking up the dual roles of studio presenter and house detective. The new series was filmed at Pinewood Studios until 2018, with series 6 filmed at the BBC Elstree Centre's Studio D in the latter half of the year. Dave Berry was a regular panellist. The first episode of the revived series aired on the same day that former host Sir David Frost died, although the news did not break until the following morning.

Before his death in August 2013, Frost gave his backing to ITV's remake, saying: "I am delighted that the Keyhole format is now entering its fourth decade on TV. I know the pilot show went down very well with the studio audience and I wish Keith and his team the very best of luck for the series."

At the start of each episode, Frost introduces a panel of three celebrities with the catchphrase "And what a panel they are ..." and some gently humorous or mocking descriptions. He then hands over to the location presenter who gives the panellists a guided tour of a property, noting particular items, though there is typically a large amount of misdirection involved as the items pointed out by the presenter are not necessarily the most pertinent clues to the person's identity. Items not specifically mentioned may provide much more useful clues. Once completed, Frost reveals the identity of the guest to the audience and the panel are given turns at guessing their identity. The audience participate with varying degrees of applause according to the accuracy of the panellists' guesswork.