Cosmology is the study of the Universe as a whole. Its overall aim is to unravel the mysteries of the cosmos by addressing fundamental questions such as why the Universe is structured in the way that we observe, how did it develop into its current form, what are its basic constituents, and what will happen to it in the future.The Cosmology and Relativity Group has an international reputation for its work in theoretical and observational cosmology, cosmological relativity and gravitational wave science, and continues to play a leading role in advancing our understanding of the nature of the Universe. Our primary research interests span a wide range of topics in modern cosmology, from theories of inflation and dark energy, gravitational waves, relativistic predictions of observables, theoretical and observational studies of the large-scale structure of the Universe, and cosmological surveys with radio and optical telescopes.Our group is heavily involved in the LISA, LIGO-Virgo, Euclid, LSST, SKA, MeerKAT, and HERA collaborations, with several of us leading work packages for these experiments. We also enjoy strong links with the String Theory Group in the Department of Physics and Astronomy and the Geometry, Analysis and Gravitation group in the School of Mathematical Sciences. We have a series of weekly seminars and discussion groups, and benefit from a busy visitor programme, which welcomes collaborators from around the world for seminars, research visits, and conferences. If you are interested in undertaking a research PhD in the group, we have a list of possible projects.