Armand Hammer, (born May 21, 1898, New York, N.Y., U.S.—died Dec. 10, 1990, Los Angeles, Calif.), American petroleum executive, entrepreneur, and art collector.

The son of a doctor, Hammer had made his first $1,000,000 through his enterprising ventures in his father’s pharmaceutical company before receiving a medical degree from Columbia University in 1921. Journeying to Soviet Russia in 1921 to give medical aid to that country’s famine victims, he was personally persuaded by Vladimir Lenin to turn his business talents to account there instead. In 1925 he obtained a concession from the Bolsheviks to manufacture pencils for the Soviet Union, and his firm soon became the largest supplier of cheap, reliable pencils in the country. His business ventures were bought out by the Soviets in the late 1920s, and Hammer returned to the United States in 1930 laden with innumerable paintings, jewelry pieces, and other art objects formerly owned by the Romanov imperial family and sold to him by the cash-hungry Soviets. In the 1930s Hammer sold the majority of these valuables and embarked on such profitable post-Prohibition business ventures as whiskey making and the manufacture of whiskey barrels, as well as cattle raising.

Tiring of his hectic business life-style, Hammer retired in 1956 but was approached that year by a friend who suggested that he finance two wildcat oil wells being drilled in Bakersfield, Calif., by the near-bankrupt Occidental Petroleum Corporation. Hammer financed the wells, which unexpectedly struck oil, and he quickly increased his holdings in Occidental, becoming the firm’s chief executive officer and chairman of the board in 1957. By the mid-1960s, under Hammer’s management, Occidental’s gross annual income was more than $650,000,000, and profitable oil ventures in Libya (which were later nationalized) and diversifications into chemical manufacturing had boosted Occidental’s gross income to more than $2,000,000,000 by 1970. Because of his longtime trade and personal contacts with the Soviets, Hammer and his firm were among the principal participants in the broadening of U.S.-Soviet trade ties that accompanied the era of detente in the 1970s. He was also a prominent art collector, and he founded the Armand Hammer Museum of Art and Cultural Center in Los Angeles in 1990 to house the bulk of his collection.