St. Augustine Catholic High School is a high school in Markham, Ontario, Canada. It is a technologically-oriented school, is part of the York Catholic District School Board, and opened in 2001. As of September 2025, it had an enrolment of 1705 students and 92 faculty members. In the Fraser Institute's Report Card on Ontario’s Secondary Schools 2025, the school was ranked 6th out of 746 secondary schools in Ontario with an overall rating of 9.6 out of 10.