Colonel The Hon. John Simcoe Macaulay (13 October 1791 – 20 December 1855) was a businessman and political figure in Upper Canada. In 1845, before retiring to England, he donated the land on which the Church of the Holy Trinity (Toronto) was built.
He was born in England in 1791, the son of James Macaulay and Elizabeth Tuck Hayter. His parents came to Upper Canada in 1792, enjoying the patronage of Lieutenant-Governor Sir John Graves Simcoe, who was also his godfather and for whom he was named. Macaulay grew up in York and attended John Strachan's school in Cornwall. In 1805, he went to England to study at the Royal Military Academy in Woolwich. He became a Captain in the Royal Engineers and served with them during the Peninsular War, seeing action at the Battle of Barrosa. He remained with his regiment until 1827, when he was appointed Professor of Fortification at the Royal Military College, Sandhurst.
When he resigned in 1835, he returned to York, Upper Canada, which had been renamed Toronto the previous year, to manage his inheritance. He made his home at Elmsley House, which had belonged (though he never lived there) to his father-in-law, and was afterwards lived in by James Bruce, 8th Earl of Elgin. Macauley became a director of the Bank of Upper Canada. In 1836, he was appointed Surveyor-General for Upper Canada by the new Lieutenant-Governor, Sir Francis Bond Head. The appointment was disputed because the candidate favoured by the Family Compact had been ignored and others did not consider Macaulay a genuine resident of the province. Head advised Macaulay to submit his resignation to the Colonial Secretary, expecting it to be refused, but it was accepted and John Macaulay, no relation, was appointed to the post instead. In 1839, he was elected to the Legislative Council of Upper Canada. Two years later, he was elected to the Toronto city council but, again frustrated by the Family Compact, he resigned after Henry Sherwood was elected mayor instead of him.