Four new dinoflagellate cyst species from the Lower and Middle Miocene strata of the Porcupine Basin, offshore southwest Ireland, are formally described. Batiacasphaera edwardsiae sp. nov. was previously described under open nomenclature from the Miocene of the adjacent Rockall Plateau. Lejeunecysta challengerensis sp. nov. is recorded sporadically from the Burdigalian and Serravallian. Selenopemphix porcupensis sp. nov. and Trinovantedinium henrietii sp. nov. are large-sized dinoflagellate cysts with maximum dimensions of approximately 100 μm. Selenopemphix porcupensis sp. nov. is recorded in the uppermost Burdigalian and Langhian, and Trinovantedinium henrietii sp. nov. is present in the Langhian and lowermost Serravallian. Batiacasphaera edwardsiae sp. nov. is possibly biostratigraphically significant for the Middle Miocene.