Montecaris is a genus of extinct phyllocarid crustaceans found in the Upper Devonian of Europe, Canada, and Australia.
Montecaris possesses an unornamented, bivalved carapace which terminates in a spiny posterior. Its caudal tail fin is trifurcated and dagger-like. Species of Montecaris from Europe and Canada are no more than in length, while M. gogoensis from the Gogo Formation of Australia can reach lengths of and, rarely, up to .
Due to its streamlined carapace and large tail fin, Montecaris was likely an active nektonic swimmer, which primarily appears in deep water sediments. Its robust mandibles and powerful musculature suggests a carnivorous lifestyle as an active predator or scavenger.