Sir Ernest Oppenheimer KStJ (22 May 1880 – 25 November 1957) was a diamond and gold mining entrepreneur, financier and philanthropist,[1][2][3] who controlled De Beers and founded the Anglo American Corporation of South Africa.

[5]: 13  He began his working life at 17, when he entered Dunkelsbuhler & Company, a diamond brokerage in London.

[5]: 13  His efforts impressed his employer and in 1902, at the age of 22, he was sent to South Africa to represent the company as a buyer in Kimberley, of which he went on to become the mayor from 1912 to 1915.

[5]: 13 [6] In this role, he helped raise the manpower for the Kimberley Regiment for service during World War I.

[5]: 13  In 1927, Oppenheimer managed to gain control of the late Cecil Rhodes' De Beers empire, building and consolidating the company's global monopoly over the world's diamond industry until his retirement.

In 1964, the Oppenheimer Diamond was named in his honour by its owner, Harry Winston, who donated the stone (not a gem, as it remains uncut and unpolished) to the Smithsonian Institution as a memorial.