Sponges from Rathlin Island, Northern Ireland were sampled during a six week SCUBA diving expedition. One hundred and twenty-eight species were recorded, 29 of which were previously undescribed. With previous records a total of 134 species are now known from Rathlin, the richness of its sponge community makes it a key site for sponges in Europe. Eight new species are described: Axinella parva, Spongosorites calcicola, Crella plana, Phorbas punctata, Lissodendoryx (Ectyodoryx) jenjonesae, Antho (Antho) granditoxa, Hymeraphia breeni and Hymeraphia elongata and information is given on the poorly known species Axinella pyramidata, Myxilla (Styloptilon) ancoratum, Antho (Antho) brattegardi, Clathria (Microciona) laevis and Plocamionida tylotata. Extension of the range of Hexadella racovitzai is discussed. A small bay of particularly high nature conservation importance for sponges was identified, many of the rarer species were limited to this area. Sponge populations on the east coast of Rathlin seem to have been damaged by dredging.