Benjamin Brewster (June 30, 1828 – August 23, 1897) was an American industrialist, financier, and one of the original trustees of Standard Oil.
Brewster was born in 1828 in Norwich, Connecticut, to Patrick Brewster (fourth great-grandson of Mayflower Pilgrim William Brewster) and Catharine Fanny Roath. He attended public schools in Norwich and went to work as a clerk in New York City.
In 1849 he headed West to join the California Gold Rush, establishing a general mercantile store in San Francisco soon after his arrival. His partner in this enterprise was Oliver Burr Jennings, and together they amassed a considerable fortune.
Brewster returned East in 1874 and settled permanently in New York City. Following his former partner Oliver Burr Jennings, who had married the sister of William Rockefeller's wife, he became involved with John D. Rockefeller in organizing the Standard Oil Company. When the Standard Oil Trust was formed in 1882 he served as a trustee.
Brewster was prominently associated with the building of the Manhattan Elevated Railway and was also a financial leader in many large railroad transactions, particularly the reorganization of the Chicago, St. Paul, Minneapolis and Omaha Railway. He served as vice president of the Chicago, Rock Island and Pacific Railroad and was a director of the Chicago and Eastern Illinois Railroad and the Delaware and Hudson Canal Company. He was also a director of the International Navigation Company, owner of the American Line of steamers.