Robert Statham Williams (May 6, 1859 – March 14, 1945) was an American bryologist who specialized in the mosses of the Yukon and South America.

[2] Williams, captivated by ornithology, prepared an almost complete set of taxidermied skins of birds from Minnesota.

He sold his collection to the Minnesota Museum of Natural History to fund his later explorations, a decision which he regretted later in life.

While living in Montana, Columbia College, on behalf of Elizabeth Britton, gave Williams a grant to collect bryophytes in the area.

He arrived at the New York Botanical Garden with his plant collections and determinations, and was hired as a museum aide by Nathaniel Britton.

He worked as a botanist for an exploration party, collecting seeds and materials from more than 200 species of vascular plants found in the Amazon basin for use by the Garden.