Nicholas Ernest de Firmian (born July 26, 1957) is an American chess player who received the FIDE title of Grandmaster (GM) in 1985.

De Firmian was a founding member of Prochess, a grandmaster advocacy group dedicated to promoting chess in the United States.

He also helped prepare the chess opening book for the IBM Deep Blue team for its successful 1997 match with Garry Kasparov.

The edition was harshly criticized by chess historian Edward Winter, who claimed that de Firmian "destroyed" the book by changing Capablanca's writing and removing games from previous editions to include new games not played by Capablanca.

White gains an overwhelming material advantage even if Black avoids immediate checkmate with precise defense.