Sir Oliver Mowat Collegiate Institute is a public high school located in Toronto, Ontario, Canada. It is located in the Port Union neighbourhood of the former suburb of Scarborough. Now part of the Toronto District School Board, the school was opened in 1969 by the Scarborough Board of Education.
The school is named after Oliver Mowat, the Premier of Ontario from 1872 to 1896. Its motto is De Monte Alto ("From a mount high").
The school was built in 1969 and was opened on September 8, 1970, as the fourteenth collegiate institute for Scarborough. The school officially opened on April 30, 1971. Mowat named for Sir Oliver Mowat, a Father of Confederation and former Ontario premier. As of April 2015, there were 1077 students enrolled at Mowat. The school originally celebrated its 50th anniversary in April 2020 but COVID-19 pandemic restrictions prevented celebrations from taking place.