Apart from Grimsby Town (now in D3N) and Crystal Palace (promoted to the Second Division), all the remaining members of the former Third Division are transferred to D3S. Two new clubs are elected to this division: Aberdare Athletic (1921–1927) and Charlton Athletic.
30 June – North Melbourne disbands in an attempt to merge with VFL club Essendon and is disqualified from the rest of the VFA season; the merger is precluded by a veto by the government of Essendon moving to Arden Street.
2 July — boxing's first “million dollar gate” occurs when Jack Dempsey meets Georges Carpentier in a “hastily assembled outdoor arena built on a farm in Jersey City, New Jersey”. A crowd of more than 80,000 attends an event billed by its promoter Tex Rickard as the "Battle of the Century". Dempsey wins by a fourth-round knockout in a scheduled 12-round fight which is also special for its radio broadcast. It is the first-ever broadcast to a "mass audience" with ringside commentary relayed over the new radiophone to hundreds of thousands of people in the northeastern United States.[2]
England tours Australia and becomes the first team to lose every match in a five-match Test series. In the 1921 English season, Australia emphasises the post-war superiority that it owes, in particular, to the pace duo of Jack Gregory and Ted McDonald. Having won 5–0 in Australia the previous winter, the Australians win the first three Tests of the 1921 tour and then draw the last two.