Sir John A. Macdonald Collegiate Institute[1] is a secondary school in Toronto, Ontario, Canada.

Sir John A. Macdonald Collegiate Institute was designed by the architectural firm, Gordon S. Adamson and Associates.

During construction, O'Sullivan was renamed to Sir John A. Macdonald Collegiate Institute, after Canada's first prime minister, John A. Macdonald, in which the colours red, black, white and purple were chosen, with the latter colour taken from the $10 Canadian banknote.

As its eleventh collegiate, the school's main building was then extended to have more classrooms, along with larger rooms used for music, art, and autoshop.

The committee's initial report recommended that three schools, including Sir John A MacDonald Collegiate, should immediately be considered for renaming.