Warwick Windridge Armstrong was an Australian cricketer who played 50 Test matches between 1902 and 1921. An all-rounder, he captained Australia in ten Test matches between 1920 and 1921, and was undefeated, winning eight Tests and drawing two. Armstrong was captain of the 1920–21 Australian team which defeated the touring English 5–0: one of only three teams to win an Ashes series in a whitewash.

In a Test career interrupted by the First World War, he scored 2,863 runs at an average of 38.68, including six centuries, and took 87 wickets. He was inducted into the Australian Cricket Hall of Fame in 2000. Armstrong was a large man (6 foot 3 inches – 1.9 m tall and 21 stone – 133 kg or 294 lb) and was known as the "Big Ship". He was not a stylish batsman but his strokeplay was effective, with a sound defence and temperament. He bowled leg spin with a gentle action and while not a big turner of the ball, he relied on accuracy to dismiss opponents.

Armstrong made his Test debut in 1902 against England at the Melbourne Cricket Ground (MCG) and was selected to tour England later that year where he was named as one of the Wisden Cricketers of the Year. That was the first of four tours of England. He was involved in several altercations with cricket administrators and was one of the "Big Six" who boycotted the 1912 Triangular Tournament in England after a dispute with the Australian Board of Control for International Cricket.

Armstrong was born in the rural Victorian town of Kyneton in 1879. The Armstrong family moved to Melbourne in 1880, settling in the inner suburb of Emerald Hill, Victoria. An inheritance enabled the family to move to a larger house, "Arra Glen" in North Caulfield, Victoria in 1888. Armstrong attended Cumloden School, a respected sporting member of the Schools Association, a group of smaller private schools in Melbourne. By 1893, he had found himself a spot in the school XI and came to the attention of the press, joining the nearby Caulfield Cricket Club and played in a senior premiership with the club at the age of 15.

The next year, the St Kilda Cricket Club, one of the leading clubs in Melbourne's pennant competition, gave the youthful Armstrong a trial. In the 1896/97 season, Armstrong fell out with St Kilda and returned to Caulfield. His last years of school were at University College. Leaving school at 19, Armstrong joined his father's former club, South Melbourne, captained by Australian Test captain Harry Trott. Armstrong was an immediate success, scoring 101 runs against University and 173 against his former club, St Kilda.

Armstrong began regular Sheffield Shield cricket in the 1899–1900 season. In his first match against New South Wales in January 1900, he dismissed Syd Gregory with his second delivery and scored 45 runs in the second innings. In the Pennant season for South Melbourne, Armstrong scored 665 runs at an average of 95; this included 145 and 6/19 against the Melbourne Cricket Club, the largest club in Melbourne whose team included many Test and first-class cricketers. Following his feats against it in 1899/1900, Armstrong was recruited for the next season by the Melbourne Cricket Club (MCC). For the next twenty years, on and off the pitch, Armstrong's fortunes were tied to the club.

The England cricket team toured Australia to compete for the Ashes in the summer of 1901/02. The English were considered a poor team, but it surprised all by winning the first Test at the Sydney Cricket Ground by an innings and 124 runs. Before the second Test, Armstrong had an excellent all-round performance against New South Wales, dismissing Test players Victor Trumper and Syd Gregory, and then scoring 137 in reply. When the team for the Melbourne Test was announced, Armstrong was selected. Australia won the Test by 229 runs. Armstrong played in the remaining Tests in the series, narrowly heading the averages with 159 runs at an average of 53, and Australia went on to win comfortably by four matches to one.

Armstrong was selected as part of the Australian cricket team to tour England in 1902. He started the tour well, taking 8/47 in the second innings against Nottinghamshire. The rest of the close-fought series was followed with interest by the English public. The final two Tests were nail-biters – Australia winning the fourth at Old Trafford by only three runs and England earning a consolation victory in the fifth Test at the Oval by one wicket. Armstrong had a good tour, making 1,075 runs at 27.56 and taking 72 wickets at an average of 17.90, but the star for the Australians was Victor Trumper, who made 2,570 runs at an average of 48.49 including eleven centuries.

On the return trip to Australia, the touring team stopped in South Africa to play three Tests, the first between the two nations. In the second Test at Johannesburg, Armstrong scored 159, just over half the Australian score of 309 and carried his bat through the innings as Australia won the Test by 159 runs. Australia won the Test series two–nil. On return to Australia for the 1902/03 season, he made 580 runs at an average of 58 and took 23 wickets. The highlights of his season included 145 against Queensland and a hat-trick against NSW.

The 1905 Australians left for England, leaving behind the beginnings of a conflict between players and administrators over control of cricket that would poison the sport in Australia for the next ten years. Australia's lack of effective bowling options had Armstrong forced to bowl wide outside the leg stump in an early form of leg theory bowling to prevent the England batsmen from scoring quickly. He maintained an accurate line and length, and put a strangle on both England's run-scoring and the crowd's entertainment and lead to what was seen by spectators and the press as dull cricket. Armstrong's tactics were ultimately futile, a Stanley Jackson-inspired England winning the series by two Tests to none.

When the team returned to Australia, the rift between the players and the Board of Control widened. The dispute saw the English postpone their tour, scheduled for 1906/07. In the midst of all this turmoil, Armstrong continued to impress: on tour with Melbourne Cricket Club in New Zealand, he was described by that country's Herald newspaper as a "team almost in himself". He made 868 runs at an average of 124 to complement his 83 wickets at under ten. He was elected captain of Victoria by his teammates for the match against NSW, commencing on New Year's Eve, responding with 6/68 with the ball and then scoring 168 in the second innings as part of a sturdy rearguard effort.

The scheduled tour postponed from the previous season kicked off with the arrival of an English team weakened by the withdrawals of a number of leading players. The first Test saw an Australian victory, Armstrong bowling 53 overs and taking four for 92. More squabbling, this time over expenses, followed between Armstrong and the VCA, and the former withdrew from the Boxing Day match against New South Wales. Armstrong sought a £1 per diem, but the VCA held fast at ten shillings. The fracas did not affect his form, however: the second Test, starting on New Year's Day, saw Armstrong score 31 and 77 and take 5 for 89. Despite his efforts, England won a hard-fought Test by one wicket. Australia took the third Test in Adelaide, and a patient 133 in 289 minutes from Armstrong in the fourth saw Australia clinch the series and win back the Ashes.

Once again, the selection and management of the Australian team to tour England in 1909 caused friction between leading players and the Board of Control. Clem Hill, unwilling to tour on the terms offered by the Board, withdrew his name from consideration. Regardless, the tour was a success, both for the Australians, who won the series two-one, and for Armstrong, who made 1,451 runs at an average of just under 44 and took 133 wickets at an average of 16.40.

The English team returned to Australia the following season to compete for the Ashes with Pelham Warner once again captain of a very strong English team that included bowlers Sydney Barnes and Frank Foster. In the second Test at Melbourne, Armstrong played one of his best Test innings. Facing exceptional bowling from Foster and Barnes, he made a nerveless 90, including 14 boundaries, before being dismissed by Foster. The hostility between the players and the board saw a fist fight break out between Clem Hill and Peter McAlister at a selection meeting. When the Board announced that George Crouch would be manager of the Australian team for the 1912 Tournament in England, rather than the player's choice, Frank Laver, outright rebellion ensued. Armstrong, Hill and Trumper, along with Hanson Carter, Tibby Cotter and Vernon Ransford (known as the "Big Six") announced that they would be unavailable to join the touring. International cricket was placed on hold as a result of the outbreak of the Great War. Armstrong had been named captain of the Australian team to tour South Africa in 1914–15, however the tour was unable to take place.

When international cricket resumed after WWI, Armstrong, now over forty years of age, was appointed captain of a strong Australian team boosted by the inclusion of players such as Jack Gregory and Herbie Collins who had starred in the Australian Imperial Forces cricket team. Armstrong was much older than many of his teammates and was the subject of some awe. The touring English team, captained once again by Johnny Douglas was no match for the Australians, who won all five Tests in the 1920/21 series, completing the first and only Ashes whitewash for 86 years. Against English teams badly affected by the Great War, the Australians dominated the series. Armstrong marshalled his troops well, utilising Gregory and Ted McDonald to devastating effect. Australia won the first Test in two days, the second Test by lunch on the third day and the third Test and the Ashes by 5.00 pm on the third day.

By the fifth Test, the Australian team was in sight of being the first Australian team to remain unbeaten throughout a tour of England. In the last three hours of the Test, Armstrong decided to rest his key bowlers and allowed his part-time bowlers to rotate as they pleased and fielders to configure themselves. During this time, Armstrong picked up a newspaper that had been blown across the field and began to read it. When asked about this later, Armstrong was said to have replied, "I wanted to see who we were playing". Despite the two losses, the tour was a triumph for Armstrong. Personally, he achieved the 1,000 runs and 100 wickets milestone for the third time in an English summer.

The 1921 tour was Armstrong's swan song in first-class cricket. On the journey back to Australia, he suffered a relapse of the malaria that had plagued him since his earlier visit to Malaya. This kept him from taking part in any of the matches in South Africa, allowing Herbie Collins to captain Australia for the first time. Armstrong resigned from his job with Melbourne Cricket Club and drawing on contacts he had made while on tour took a role as an agent for Dawson's Scotch Whisky. He remained in the liquor trade until his retirement in 1946.

A talented Australian rules footballer, Armstrong briefly represented South Melbourne in the Victorian Football League before playing Test cricket. For much of his cricket career he was employed as a pavilion clerk by the Melbourne Cricket Club, who allowed him time off to play cricket. Following his retirement from Test and first-class cricket after the successful 1921 tour of England, Armstrong wrote on cricket for the Sydney Evening News. Armstrong, following illness that saw him lose much of the weight that he was known for, died on 13 July 1947, leaving an estate to the value of £90,000.