Sir John George Tollemache Sinclair, 3rd Baronet (8 November 1825 – 30 September 1912) was a Scottish landowner and Liberal politician who sat in the House of Commons from 1869 to 1885.

Born in Edinburgh in 1825, he was the son of Sir George Sinclair, 2nd Baronet, and Lady Catherine Camilla Tollemache, daughter of William Talmash, Lord Huntingtower.

[5] Before their marriage was dissolved in 1878, the couple had two sons and two daughters:[6] Sir John died on 30 September 1912.

As he was predeceased by his eldest son Clarence, he was succeeded in the baronetcy by his grandson Archibald Henry Macdonald Sinclair, who was later created Viscount Thurso in 1952.

[12] Sinclair was the earliest born person to have made a gramophone disc recording.