The 1921 Perth Carnival was the fourth edition of the Australian National Football Carnival, an Australian rules football interstate competition, staged in August 1921. It was the first carnival to take place in Perth and was won by the home state, Western Australia.
The decision to stage the carnival in Perth represented a significant additional expense for the carnival, as the transcontinental travel expenses for the visiting states was much higher. New South Wales and Queensland quickly withdrew, and Tasmania equivocated but ultimately decided likewise, resulting in a small carnival of only three teams. Nevertheless, the council saw benefit in staging the carnival in Perth to consolidate the strength of Australian rules football in the city, as it had seen post-war growth in the popularity of soccer as a rival code.
Ultimately, the carnival made a good profit, with a total gate of £5530 more than covering the visiting teams' travel expenses of £2000. The crowd of 26,461 drawn to the final match between Western Australia and South Australia set a new record for the highest sports attendance in Western Australian history.