Gridley Bryant (1789 – June 13, 1867) was an American construction engineer who ended up building the first commercial railroad in the United States and inventing most of the basic technologies involved in it.

Investigating how to move the granite needed for these projects from the quarry in Quincy to the work sites, he concluded that the best method would be via a railroad, much like that of the Liverpool and Manchester Railway which was still in the planning stages at the time.

A reluctant state legislature granted Bryant a charter to build a railroad with Bunker Hill monument director Thomas Handasyd Perkins as the principal financier and owner of a majority of the shares.

He used similar developments and technologies that had already been in use on the railroads in England, but he modified his design to allow for heavier, more concentrated loads and a three-foot frost line.

Bryant was called upon as an expert witness by the Baltimore and Ohio Railroad in an effort to invalidate Winans' patent.