Alliston is a settlement in Simcoe County in the Canadian province of Ontario.
It has been part of the Town of New Tecumseth since the 1991 amalgamation of Alliston and nearby villages of Beeton, Tottenham, and the Township of Tecumseth. The primary downtown area is located along Highway 89, known as Victoria Street.
The town grew as a commercial centre for the area farmers and was best known as a potato-growing area. It is still a major industry in the town and is celebrated by the annual Alliston Potato Festival. Honda of Canada Manufacturing operates a large auto manufacturing facility southeast of Alliston, currently consisting of three major factories. In the 2016 census, the town of Alliston grew by 25% since 2011 to 19,243 residents making it one of the top 10 fastest growing communities in Canada.