Robert Frederick Foster (May 31, 1853 – December 25, 1945) of New York City, known as R. F. Foster, was a memory training promoter and the prolific writer of more than 50 nonfiction books. He wrote primarily on the rules of play and methods for successful play of card, dice, and board games.  Alan Truscott wrote 20 years after his death that Foster "had been one of the great figures in whist and bridge" for 60 years.