Charles Willison Johnson (October 26, 1863 – July 19, 1932) was an American naturalist who specialized in entomology (especially Diptera) and malacology, making significant contributions in both fields.

He was a mentor and inspiration to many students and young scientists such as William J. Clench (who founded a publication named Johnsonia in his honor).

He assisted Henry Augustus Pilsbry with The Nautilus, an important American malacological publication.

At age 17 he moved to St. Augustine, Florida, and threw himself into an intensive and energetic study of the area's fauna.

His activity caught the eye of Joseph Willcox, a trustee of the Wagner Free Institute of Philadelphia, who was in Florida on a field trip.