Captain Britain is a British comic feature published by Marvel UK – the British division of Marvel Comics between 1976 and 1985, in various anthology magazines.

The first of these was named after the strip and debuted the first incarnation of Captain Britain, Brian Braddock. The strip was revived in 1980 and appeared in various British comics before headlining a second eponymous series in 1985. After this was cancelled in 1986, many of the characters and concepts were incorporated into the Marvel Comics series Excalibur.

Marvel UK had been established in 1972. In order to fit in with the style of British weeklies, titles such as The Mighty World of Marvel consisted of reprinted Marvel material in an anthology magazine format, with much of the colour removed. However, these failed to make a major impression on the market, which was dominated by titles of original British material from Fleetway Publications and DC Thomson. In response, Marvel decided the line needed a British character as a flagship title. As Marvel UK itself was effectively a packaging operation at the time with no experienced creative staff the character was devised at Marvel's American headquarters. London-born Chris Claremont - at the time a rising star in the company following his successful work on the revival of X-Men - was one of the few Anglophiles on staff, and was assigned to the title. He came up with the name, origin and cast for the new title, Captain Britain. Art duties went to experienced Incredible Hulk artist Herb Trimpe, who lived in Cornwall at the time and would recall the 8-page strips typically only took him a couple of days to draw. The designer of the character's patriotic costume, complete with Heraldic lion rampant, is unknown; Trimpe has speculated it was John Romita. The character's origin tied into British Arthurian myths, seeing 'Thames University' science student and part-time laboratory assistant Brian Braddock granted the powers and identity of Captain Britain by Merlyn and his daughter Roma after a motorcycle accident on Darkmoor. The latter was inspired by Dartmoor, site of a fact-finding vacation for Claremont and Trimpe. The new character debuted in Captain Britain #1. After the first two issues covering Braddock's origin, Captain Britain #3 introduced the initial supporting cast - love interest Courtney Ross; campus bully Jacko Tanner; and Inspector Dai Thomas, a Scotland Yard CID officer with a deep hatred of superheroes who continually tried to expose Captain Britain as a menace and discover his secret identity, and who was often gently undermined by more reasonable subordinate Kate Fraser. Claremont would later note the set-up was deliberately reminiscent of Spider-Man, considering the format to be "intro to Marvel 101".

The title launched with some fanfare, even garnering reviews (albeit a negative ones) in The Financial Times and The Daily Record. The strip was in full colour, and in keeping with the anthologies common on the British market featured only eight pages of Captain Britain, with the magazine being filled out by reprints of Fantastic Four and Nick Fury, Agent of S.H.I.E.L.D.. In common with another quirk of the British market, the first issue featured a free gift - a cut-out-and-wear paper version of the hero's mask. Marvel arranged a visit to the UK by Stan Lee to promote the title; however, it was ill-timed as British comics were soon to be caught up in a moral panic. Fleetway's anarchic Action had rapidly grabbed British tabloid attention with its violent content, and was soon on the radar of Mary Whitehouse, a self-appointed moral guardian of the British public. This led to questions about the medium being asked in the House of Commons and Fleetway editor John Sanders being excoriated by host Frank Bough on the prime-time BBC One magazine show Nationwide. The British press, with little knowledge or interest in the medium, lumped Captain Britain in with Action despite its more wholesome content, and Lee's whistle-stop tour also saw him questioned about the violence in comics.

Captain Britain #8 would introduce Brian's twin sister, model Elizabeth "Betsy" Braddock, who was revealed to have psychic powers, with the following issue debuting Jamie Braddock, their playboy racing-car-driving older brother. However, Claremont left the title after the tenth issue; accounts differ as to whether this was due to the logistical difficulties of working on the title when fax and courier services were in their infancy, or through disputes with title editor Larry Lieber. His replacement was Gary Friedrich, best known for his role in the creation of Ghost Rider. Friedrich had also had a stint writing Sgt. Fury and his Howling Commandos and added the modern incarnation of the lead to Captain Britain as a guest character; subsequent storylines featured Captain America and the Red Skull, firming up the strip's connection to the Marvel Universe. In Captain Britain #17, Friedrich also established the British equivalent of S.H.I.E.L.D. - Special Tactical Reserve for International Key Emergencies or S.T.R.I.K.E. for short.

Due to most of the staff involved having only visited Britain as tourists, stories attempted to appeal to a British audience by featuring prominent London location such as Heathrow Airport, Regent Street and Big Ben, or figures such as the Queen, especially the forthcoming Silver Jubilee and then-British Prime Minister James Callaghan, who made several guest appearances. Paul Neary would later note that these were a major weakness of the series, doing nothing to tie the character to modern-day British readers. Sales were moribund, and Captain Britain went to black-and-white from #24 to cut costs, attempting to soften the blow with another free gift - Captain Britain's lesser-spotted 'Superjet'. Alan Davis would also recall that - unknown to the American creative team - the 'lion mark' had previously been used by the Egg Marketing Board to denote the quality of eggs, leading to many jokes at the character's expense. In a 1986 article for Amazing Heroes, N.A. Collins named Captain Britain's first costume among the six worst male superhero looks in comic history up to that point, noting the "weird sunroof mask" and the "tacky Avon jewellery".

Sales failed to improve, and after 39 issues Captain Britain was merged with Marvel UK's Spider-Man reprint title, at the time called Super Spider-Man. Captain Britain was initially featured on the front page of Super Spider-Man and Captain Britain #231 alongside the web-slinging hero, but as the weeks went on would occupy only a small corner of a handful covers. By this point Friedrich and Trimpe had also left and the strip would be subject to several creative teams made up of Marvel staffers, with contributors including Lieber, Bob Budiansky and Ron Wilson, leading to a drastic fall in quality and consistency. A hardback annual, compiling selected reprints from the weekly title, was also produced.

Meanwhile, Captain Britain had already appeared alongside Spider-Man in America. Claremont was working on Marvel Team-Up with John Byrne and decided to use the format as an introduction for Braddock via the device of him briefly rooming with Peter Parker. The two-issue storyline also saw the debut of Arcade and his Murderworld. However it was not enough to raise any immediate interest in the character from American readers, and in Britain a black-and-white reprint of the Marvel Team-Up issues (split into three episodes apiece) ended Captain Britain's run in the pages of Super Spider-Man, concluding in #253 (dated December 14, 1977) a little over a year after the character's debut.