Quigley, Phillips, Thys Read full paper. Abstract The ocean sunfishes are currently represented by five species within three genera: Mola mola (Linnaeus, 1758), Mola alexandrini (Ranzani, 1839), Mola tecta (Nyegaard, Sawai, Gemmell, Gillum, Loneragan, Yamanoue & Stewart, 2017) (Sawai et al., 2018), Masturus lanceolatus (Lienard, 1840), and Ranzania laevis (Pennant, 1776). Growing conservation concerns have led to an ongoing re-examination of their classification status on the International Union for the Conservation of Nature Red Lists, a process requiring the latest data to best support their conservation management on a global scale. Here we report the first sighting of Masturus lanceolatus in the northeast Irish Sea, representing a new northerly range limit for this species in the northeast Atlantic. The species is more commonly reported in tropical seas, and in the Western Atlantic they occur from North Carolina in the United States to southeast Brazil. This sighting increases the most northerly range limit by 2610 km, providing additional insight into the ecology and potentially changing distribution of this generally considered tropical megafaunal species. KEYWORDS Molidae, range expansion, stranding, sunfish