John Sebastian Helmcken (June 5, 1824 – September 1, 1920) was a British Columbia physician who played a prominent role in bringing the province into Canadian Confederation.

Helmcken arrived on Vancouver Island in March 1850 and was posted first to Fort Rupert, where he was soon made a magistrate and tasked with resolving a dispute between the company and the coal-miners there, who wanted to join the California Gold Rush and had gone on strike.

Six months later, Chief Factor James Douglas called Helmcken to Fort Victoria to attend the ailing Governor Richard Blanshard, and he settled there permanently.

Douglas was by that time the governor of the colony, and Helmcken had effectively joined what newspaperman Amor de Cosmos called disparagingly the "family-company compact".

Helmcken was in favour of British Columbia joining Canadian Confederation for a while in 1866, but by the time the issue was being seriously debated in 1870, he had dismissed it as impractical and against the financial interests of the colony.

"[3] Despite his opposition to the idea, Helmcken was sent along with Joseph Trutch and Robert Carrall to Ottawa to negotiate terms of confederation with the Canadian government.