Sir John Sparrow David Thompson was a Canadian lawyer, judge and politician who served as the fourth prime minister of Canada from 1892 until his death. He had previously been fifth premier of Nova Scotia for a brief period in 1882.

The prime minister of Canada is the head of government of Canada. Not outlined in any constitutional document, the office exists only per long-established convention. Under the Westminster system, the prime minister governs with the confidence of a majority of the elected House of Commons; as such, the prime minister typically sits as a member of Parliament (MP) and leads the largest party or a coalition of parties. The prime minister is appointed by the monarch's representative, the governor general, and, as first minister, selects other ministers to form the Cabinet and chairs it. Constitutionally, executive authority is vested in the monarch, but, in practice, the powers of the monarch and governor general are nearly always exercised on the advice of the Cabinet, which is collectively responsible to the House of Commons. Canadian prime ministers are appointed to the Privy Council and styled as the Right Honourable, a privilege maintained for life.