Polarornis is a genus of prehistoric bird, possibly a loon. It contains a single species Polarornis gregorii known from incomplete remains of one individual found on Seymour Island, Antarctica, in rocks which are dated to the Late Cretaceous (López de Bertodano Formation, about 66 mya). The discovery of Polarornis gregorii was first announced by Sankar Chatterjee in 1989, but he did not describe and officially name the species until 2002. The name Polarornis had been announced unofficially several years prior to its official publication, in Chatterjee's 1997 book The Rise of Birds.