An Act Against Slavery was an anti-slavery law passed on July 9, 1793, in the first legislative session of Upper Canada, what is now Ontario. It was the first anti-slavery legislation in the British Empire.
While limited in scope -- it allowed existing slavery to continue -- the Act was a major, and controversial, step towards the end of slavery in North America. It made Canada a safe haven for escaped American slaves.
John Graves Simcoe, Lieutenant Governor of Upper Canada, had been a supporter of abolition before coming to Upper Canada; as a British Member of Parliament, he had described slavery as an offence against Christianity.