Corylus johnsonii is an extinct species of hazel known from fossil fruits found in the Klondike Mountain Formation deposits of northern Washington state, dated to the early Eocene Ypresian stage (56 to 48 million years ago).

The description of this species by paleobotanists Kathleen Pigg, Steven Manchester, and Wesley Wehr was based on the study of thirty-four compression fossil specimens found at the UWBM sites B4131 and A0307, the latter being designated the type locality.

[1] The species epithet johnsonii was coined in honor of Kirk R. Johnson for his continuing work on, and recognition of the importance of, the Republic Flora.

[1] Though described as a single species, Pigg et al noted the wide grade of variation in the involucre morphology, ranging from simple to ones with extensive spines.

As specimens of C johnsonii have a full morphology range between the three involucre types, the possibility of multiple species is hard to prove or disprove.