Peter Thomas Gallagher FRAS FTCD MInstP is an Irish astrophysicist. He specialises in solar physics, notably solar storms and their impact on the Earth. He is Senior Professor, and Head of Astronomy and Astrophysics, at the Dublin Institute for Advanced Studies, director of Dunsink Observatory, and an adjunct professor at Trinity College Dublin. He is also the head of the radio-telescope project I-LOFAR, at Birr Castle. He is widely cited in his field and often quoted in the media.