Isaac "Jack" Barnato Joel (29 September 1862 – 13 November 1940) was a British -South African mining magnate and a champion horse breeder.

[5] Joel served as Chairman of Johannesburg, South Africa Consolidated Investment Company Ltd from 1931 until his death in 1941.

He also had a large interest in Diamond Corporation Ltd. and the De Beers Consolidated Mines, Ltd.[6] Beginning in 1900 when he registered his colours of 'black jacket, scarlet cap',[7] he was a thoroughbred racehorse owner and breeder,[6] who won The Derby twice, first in 1911[8] with Sunstar in front of the King and Queen,[9] and second in 1921 with Humorist.

[13] Joel married Edith Fanny Richards (1866–1901), with whom he had three children: In 1907,[17] after Edith's death, he married Olive Coulson Sopwith (1876–1937),[18] daughter of Thomas Sopwith,[19] an English mining engineer and local historian.

[21] In his will, he stated that he was unable to leave any charitable donations because of the "crushing burden of present-day taxation.