Orillia (IPA: ōrĭl'ēə) is a city located in Simcoe County in Southern (South-Central) Ontario, Canada, between Lake Couchiching and Lake Simcoe, 135 kilometres (84 mi) north of Toronto.

Originally incorporated as a village in 1867, the history of what is today the City of Orillia dates back at least several thousand years. Archaeologists have uncovered evidence of fishing by the Huron and Iroquois peoples in the area over 4,000 years ago as well as sites used by Native Americans for hundreds of years for trading, hunting, and fishing.

Known as the "Sunshine City", the city's large waterfront attracts many tourists to the area every year, as do a good number of annual festivals and other cultural attractions. While the area's largest employer is Casino Rama, overall economic activity in Orillia is a mixture of many different industries including manufacturing, government services, customer service and tourism.

The site of an Ojibwa reserve from 1830 to 1838, Orillia subsequently prospered as an agricultural and lumbering community. Transportation links with Toronto and Georgian Bay stimulated Orillia's development as a commercial centre and summer resort. The village of Orillia was incorporated in 1867 (sharing the same birthyear as Canada), became a town in 1875, and was designated a city in 1969. The city of Orillia is located on the shores of two connected lakes: Lake Simcoe and Lake Couchiching. Both lakes are part of the Trent-Severn Waterway. Travel north on Lake Couchiching, then through three locks and the only marine railway in North America leads to Georgian Bay on Lake Huron. Travel south-east across Lake Simcoe, through many locks (including two of the highest hydraulic lift locks in the world) eventually leads to Lake Ontario. From either of these Great Lakes one can connect to the St. Lawrence and thence to the Atlantic Ocean.