Thomas Simpson (July 2, 1808 – June 14, 1840) was an arctic explorer, Hudson's Bay Company agent and cousin of HBC governor Sir George Simpson. His violent death in what is now the state of Minnesota—allegedly by suicide after gunning down two traveling companions in the wilderness—has long been a subject of controversy.
Simpson was born in Dingwall, Scotland the son of magistrate Alexander Simpson (1751–1821) by his second wife Mary who had helped raise George Simpson. He was a sickly and timid youth, avoiding rough sport. He was educated with a view to his becoming a clergyman, and was sent to King's College, Aberdeen at the age of seventeen. Sir George Simpson offered him a position in the Hudson's Bay Company in 1826, which he declined in order to complete his studies. He graduated in 1828, at the age of 20, with a Master of Arts. He enrolled in a divinity class that winter with the goal of becoming a clergyman, when the offer of a position in the Hudson's Bay Company was again extended, and this time he accepted. In 1829 he arrived in Norway House to join the Hudson's Bay Company as George Simpson's secretary.
Simpson was stationed at the Red River Colony in the 1830s, serving as second officer to chief factor Christie.
From 1836 to 1839, Thomas Simpson was involved in an expedition to chart the Arctic coast of Canada in order to fill two gaps left by other expeditions in search of the Northwest Passage. The expedition was headed by Peter Warren Dease, a chief factor of the Hudson's Bay Company. Thomas was the junior officer but Dease ceded most of the responsibility to Simpson. Several writers present Simpson as an ambitious and over-confident young man while Dease was 20 years older, experienced in Arctic travel, efficient but perhaps under-confident. Ten more men went with them including the canoemen James McKay and George Sinclair who had been with George Back in his 1834 journey down the Back River.