James Ballantine Mercer (1842 – 4 November 1925) was a Scottish-born Australian politician.
He was born in Glasgow to tobacco spinner William Mercer and Grace Dixon.
He left school at a young age to work as a woodcarver's apprentice in Sheffield, and then worked as a lay reader for the Church of England.
He emigrated to Queensland in 1883 and moved to Sydney in 1885, working as a caretaker at the Seaman's Institute at Circular Quay.
In 1916 Mercer left the Labor Party as part of the conscription split, and he did not recontest his seat in 1917.