John Ambrose O'Brien (May 27, 1885 – April 24, 1968) was a Canadian industrialist and sports team owner.

In the 1909–10 NHA season, the Creamery Kings received the nickname "Millionaires" as O'Brien signed up several stars of the time to extravagant contracts, including Fred "Cyclone" Taylor and brothers Frank Patrick and Lester "the Silver Fox" Patrick, and acquired Edouard "Newsy" Lalonde in an attempt to win the Stanley Cup for Renfrew.

While in Montreal for business in November 1909, O'Brien was asked by the then owners of the Creamery Kings to apply to join the Canadian Hockey Association.

Outside the hotel room where the CHA meetings were occurring he met Jimmy Gardner, manager of the Montreal Wanderers.

[3] In December 2006, as the founder of the Montreal Canadiens, John Ambrose O'Brien was an inaugural inductee in the team's newly created 'Builders Row' in the Bell Centre.