Robert Hamilton Hyatt (November 1, 1884 – September 11, 1963) was an American professional baseball first baseman.

He played in Major League Baseball (MLB) from 1909 to 1918 for the Pittsburgh Pirates, St. Louis Cardinals, and New York Yankees.

Hyatt started his professional baseball career with the Vancouver Beavers of the Northwestern League.

From 1909 to 1914, Hyatt served mostly as a pinch hitter for the Pirates; Steve Treder of The Hardball Times credits him as baseball's first pinch-hitting specialist.

He spent 1920–1923 with the Pacific Coast League's Vernon Tigers, hitting over .300 each year.