Samuel Reshevsky (November 26th 1911 - April 4th 1992) learned chess when he was 4 years old. He became known as a child chess prodigy and was playing simultaneous games of chess against adults when he was 6 years of age. At age 8 he was playing chess against strong players.
The New York Times:
" Twenty graybeards sitting in a square played chess yesterday in Paris against a very small boy 8 years old, and he beat them all. Among the graybeards were some of the best players in France, and one at least, whose boast it is that he drew with Capablanca, the Pan-American chess champion, but all their reputation availed them nothing against a frail child with a pale, thoughtful face who moved quietly from one board to another, reducing their most skillful plans and wiles to nothingness and mating them and mating them when they least expected it. "