Charles Reid Barnes (1858–1910) was an American botanist specializing in bryophytes (mosses, liverworts and hornworts).

He graduated from Hanover College in 1877, and afterward studied at Harvard University, where he became friends with Asa Gray.

In 1887 he was called to the University of Wisconsin, and for eleven years developed and maintained a vigorous department of botany in that institution.

At Hanover College he met John Merle Coulter as his instructor in botany, and from that time they became intimately associated, first as joint editors of the Botanical Gazette, and later as colleagues in the same university.

Barnes died in Chicago, on February 24, 1910, from injuries sustained in an accidental fall.