Justin Lee Langer AM was perhaps the first Test opener in history to average in the mid-forties yet always be scrabbling for his spot in the side. Or at least that's the perception: in a land of dashers and crashers Langer was seen as a grafter, a battler, only ever a couple of failures away from oblivion. The reality was somewhat different. Yesteryear's ugly duckling turned into a stroke-playing swan, racking up more Test hundreds than those national treasures Doug Walters, Ian Chappell, Mark Waugh and Bill Lawry, and scoring an eye-popping 1481 runs in 2004.

Born in Perth, Western Australia, Langer excelled at cricket from an early age, representing Western Australia at under-age level, as well as the Australia under-19 team. He also won a scholarship to the Australian Cricket Academy at the Australian Institute of Sport in 1990. Langer made his first-class debut for Western Australia during the 1991/92 Sheffield Shield, and, after good form at state level, made his Test debut for Australia the following season at the age of 22, during the West Indies' 1992/93 tour. Although maintaining his place in the side, he struggled for form, and only made sporadic appearances for Australia until his selection for Australia's 1998–99 tour of Pakistan, in which he scored his first Test century.

Langer made his Test debut against the West Indies at the Adelaide Oval, in January 1993. He received a rough welcome against an in-form West Indian bowling attack, including being hit on the back of the head by his very first ball in Test cricket, delivered by Ian Bishop. Along with the rest of the Australian team, he took numerous blows from their pace bowlers. After only managing to score 20 in the first innings, Langer top-scored for Australia with 54 in the second, a famous chase by Australia that fell just 2 runs short.

Having been injured for the first four Tests, he replaced Michael Slater as Matthew Hayden's opening partner for the final Test, and scored a century in Australia's innings win. This was the first of three centuries in consecutive matches that secured Langer's position at the top of the order. Except for injuries, the partnership between Hayden and Langer (with Ricky Ponting moving to Langer's previous position at number three) persisted until Langer's retirement at the conclusion of the 2006/07 Ashes series. Their partnership included a total of 5,655 runs over a period of 113 innings, second only to the partnership between West Indians Gordon Greenidge and Desmond Haynes.

He retained his place for the following tour of New Zealand. After decent but not awe-inspiring totals in the first two Tests (63 & 24), Langer suffered the indignity of getting a pair in the third Test, falling for a duck in both innings. He was subsequently dropped, and other than a few scattered appearances did not return to the Australian Test team until October 1998, for the tour of Pakistan. In November 1999 at Bellerive Oval in Hobart, he shared a match-winning 238-run partnership with Adam Gilchrist to rescue Australia from 126/5 chasing a victory target of 369 against Pakistan. The century scored in this innings was scored in 388 minutes, an Australian record for the slowest century.

Langer was a number three batsman until 2001 when he was dropped after failing to convert a series of starts during Australia's 2–1 loss in India. During the second Test in Kolkata, he bowled a single over when V. V. S. Laxman and Rahul Dravid defied the Australian attack for the entirety of the fourth day, forcing captain Steve Waugh to try almost all his players as bowlers; it was the only time Langer ever bowled at Test level. Shortly after though, he replaced Michael Slater as an opening batsman for the final 2001 Ashes series Test at The Oval where he celebrated his return with a century. He did not get dropped again and as an opening batsman he averaged 52.38 and scored 14 centuries in 44 matches.

Langer returned to Australia in the 2002/03 Ashes series, where his very successful partnership with Matthew Hayden developed. In this series, Langer scored his top score of 250 against England at the Melbourne Cricket Ground. Langer personally outscored the entire Pakistan side in the Perth Test of 2004. He scored 191 and 97 while Pakistan made 179 and 72. It was the first occasion of a player being dismissed in both the 190s and 90s in a Test. In the 2005 Ashes series, Langer top-scored for an unsuccessful Australian team, with 391 in the series. His top score was 105, scored in the final test.

After this, pressure was mounting on the opening partnership of Hayden and Langer. Calls were coming to have the pair replaced by a younger duo, that would ensure the future and stability of the team to come. However, the partnership had support from the Australian selectors and was only disrupted in the 2006 Summer series when Langer was out with injury. He was replaced by Mike Hussey and Phil Jaques for two tests.

Langer then suffered a number of injuries, increasing the pressure on selectors to drop him for rising star Phil Jaques. Langer was selected over Jaques for the 2007 Ashes series, which turned out to be his last. Langer scored an 80 and a century in the first test, but it was slim pickings to follow for him. Despite success in the Australian Test team, he did not get recalled to the one-day team, even after he was named as the domestic ING Cup's player of the season in 2002/03.

On New Year's Day 2007, Langer announced his retirement from Test cricket after the fifth Ashes Test against England, starting at the Sydney Cricket Ground the following day. In doing so, he joined Shane Warne and Glenn McGrath who had both announced their retirements earlier in the month, and it came only three matches after the surprise departure of Damien Martyn. He came to the decision during the previous match in Melbourne, having earlier decided against retiring after the tour of South Africa to help Australia reclaim the Ashes.

Langer was the captain of the Western Warriors until the end of the 2006/2007 season. He became the highest run-scorer for Western Australia in 4-day matches, after passing Tom Moody's old record of 8853 runs on 5 December 2007 against Tasmania at Bellerive Oval. In March 2008, Langer announced his retirement from Australian first-class domestic cricket. Earlier in the year, Langer had announced his retirement from the Australian domestic one-day cricket. Despite his retirement from international cricket, Langer opted to continue to play first-class cricket, with Somerset announcing on the same day that Langer had agreed to return to the English county in 2007 as captain.

In July 2009, playing his 615th innings, he surpassed Sir Donald Bradman as the leading Australian first-class run scorer when he scored his 86th century while playing Worcestershire. At the end of the 2009 season, Langer announced that he would not be returning to Taunton in a playing capacity the following season, and retiring from all competitive cricket. He commented in an interview with BBC Somerset that he was in discussions to potentially return at some point to the county in the future in a coaching capacity.

In July 2017, Langer was appointed to the board of the West Coast Eagles football club. In May 2018, Langer was announced as the coach of the Australian national cricket team, and then in October 2019, Andrew McDonald was appointed as his assistant coach. In 2019, he coached Australia to the semi-finals of the 2019 Cricket World Cup, losing to England by 8 wickets. It was noted before the game that Langer had got Australia to walk barefoot around the edge of Edgbaston before the match in a bid to capture "positive energy coming out of the earth".