A novel Babesia species is described from blood collected from 3 common murres (also known as common guillemots) (Uria aalge) from California. This is the first report of a Babesia species from the Alcidae and the second from the Charadriiformes. Babesia uriae n. sp. is morphologically similar to several other avian Babesia species but can be differentiated from Babesia bennetti, the only other species from a host in the Charadriiformes, by size of round and amoeboid forms. Phylogenetic analysis of near–full length 18S rRNA, ITS-1, 5.8S rRNA, and ITS-2 sequences indicated that the Babesia sp. from the common murre is closely related to Babesia poelea, a parasite of brown boobies (Sula leucogaster).