John Thomas (1724 – 2 June 1776) was an American medical doctor and soldier from Massachusetts who became a major general in the Continental Army.

As a young man he studied medicine with Doctor Tufts in Medford before beginning his own practice in Kingston.

During King George's War in 1746 he was appointed surgeon to a regiment bound for Annapolis Royal in Nova Scotia.

He led his troops to the siege in Boston, and in June, the Congress appointed him a brigadier in the Continental Army.

On the night of March 4, 1776, he led his division to fortify the Dorchester Heights, overlooking the south harbor at Boston, by using cannon that Henry Knox had brought from Fort Ticonderoga.

After General Richard Montgomery was killed, Thomas was assigned to command in Canada and take charge of the Canadian invasion.