Bowseria arctowskii gen. et sp. nov., a new organic-walled monothalamous (single-chamber) foraminiferan is described from samples collected in Admiralty Bay (King George Island, West Antarctica) at 100- 200 m water-depth (mwd). The species is characterized by a large (1- 2 mm) elongate theca with a single terminal aperture. Molecular phylogenetic analyses, based on partial small subunit rDNA sequences, indicate that the new species belong to a clade of single-chambered foraminifers that branch as a sister group to the multi-chambered textulariids and rotaliids. The most closely related to the new species is an undetermined allogromiid from under the Ross Ice Shelf.