Ian Michael Chappell (born 26 September 1943) is a former cricketer who played for South Australia and Australia. Known as "Chappelli", he is considered as one of the greatest captains the game has seen. He captained Australia between 1971 and 1975 before taking a central role in the breakaway World Series Cricket organisation. Born into a cricketing family—his grandfather and brother also captained Australia—Chappell made a hesitant start to international cricket playing as a right-hand middle-order batsman and spin bowler. He found his niche when promoted to bat at number three. Chappell's blunt verbal manner led to a series of confrontations with opposition players and cricket administrators; the issue of sledging first arose during his tenure as captain, and he was a driving force behind the professionalisation of Australian cricket in the 1970s. He was the captain of the Australian squad which finished as runners-up at the 1975 Cricket World Cup.

John Arlott called him "a cricketer of effect rather than the graces". An animated presence at the batting crease, he constantly adjusted his equipment and clothing, and restlessly tapped his bat on the ground as the bowler ran in. Basing his game on a sound defence learned during many hours of childhood lessons, Chappell employed the drive and square cut to full effect. He had an idiosyncratic method of playing back and across to a ball of full length and driving wide of mid-on, but his trademark shot was the hook, saying "three bouncers an over should be worth 12 runs to me". A specialist slip fielder, he was the fourth player to take one hundred Test catches.

Since his retirement in 1980, he has pursued a high-profile career as a sports journalist and cricket commentator, predominantly with Channel Nine. He remains a key figure in Australian cricket: in 2006, Shane Warne called Chappell the biggest influence on his career. Chappell was inducted into the Sport Australia Hall of Fame in 1986, the FICA Cricket Hall of Fame in 2000 and the Australian Cricket Hall of Fame in 2003. On 9 July 2009, Ian Chappell was inducted into the ICC Cricket Hall of Fame.

The first of four sons (Ian, Greg, Trevor, Michel) born in Unley, near Adelaide, to Martin and Jeanne (née Richardson), Chappell was steeped in the game from an early age. His father was a noted Adelaide grade cricketer who put a bat in his hands as soon as he could walk, and his maternal grandfather was famous all-round sportsman Vic Richardson, who captained Australia at the end of a nineteen-Test career. Chappell was given weekly batting lessons from the age of five, as were younger brothers Greg and Trevor, who both also went on to play for Australia.

Chappell grew up in the beachside suburb of Glenelg and attended the local St Leonard's Primary School where he played his first competitive match at the age of seven. He was later selected for the South Australian state schoolboys team. He then enrolled at Prince Alfred College, a private secondary school noted for producing many Test cricketers, including the Australian captains Joe Darling and Clem Hill. His other sporting pursuits included Australian football and baseball: Chappell's performances for South Australia in the Claxton Shield won him All-Australian selection in 1964 and 1966 as a catcher. He credits Vic Richardson, who had represented both SA and Australia in baseball during the 1920s, for his love of the sport. At the age of 18, his form in grade cricket for Glenelg led to his first-class debut for South Australia (SA) against Tasmania in early 1962.

The aggressive style of Sobers and of South Australia captain Les Favell heavily influenced Chappell during his formative years in senior cricket. In 1962–63, Chappell made his initial first-class century against a New South Wales team led by Australian captain Richie Benaud, who was bemused by the young batsman's habit of gritting his teeth as he faced up; to Benaud, it looked as if he was grinning. Chappell spent the northern summer of 1963 as a professional in England's Lancashire League with Ramsbottom and played a single first-class match for Lancashire against Cambridge University.

In 1963–64, Chappell batted at number three for SA for the first time, in a match against Queensland at Brisbane, and scored 205 not out. He was the youngest member of the SA team that won the Sheffield Shield that season. A century against Victoria early the following season resulted in Chappell's selection for a one-off Test against Pakistan at Melbourne in December 1964. He made 11 and took four catches, but was dropped until the Fourth Test in the 1965–66 Ashes series. Chappell supplemented his aggressive batting with brilliant fielding in the slips, and he showed promise as a leg-spinner. At this point, the selectors and captain Bob Simpson considered him an all-rounder: he batted at number seven and bowled 26 (eight-ball) overs for the match.

He retained his place for the following Test and for the tour of South Africa in summer 1966–67. Playing in a side defeated 1–3, Chappell struggled to make an impression. His highest score in ten Test innings was 49, while his five wickets cost 59 runs each. On the advice of Simpson, he ceased playing the hook shot as it was often leading to his dismissal. In the first Test of 1967–68 against India, he failed twice batting in the middle order. Heading into the second Test at Melbourne, Chappell's place was in jeopardy, but he rode his luck to score 151 – his innings contained five chances that the Indians failed to take. However, in the remainder of the series, he managed only 46 runs in four innings, so his selection for the 1968 tour of England was based as much on potential as form.