The most important onshore Paleogene deposits of Britain are the classic sequences of the London and Hampshire basins, SE England, which have been studied almost since the first interest in rocks and fossils developed in this country. Ostracods were identified and reported from these sequences relatively early (e.g. Jones 1854), following shortly after the key stratigraphical works of Joseph Prestwich published between 1846 and 1855, although not as early as continental workers recorded Cenozoic ostracods (e.g. Minster 1830). At the time of writing the authors are not aware of any significant published records of British Paleogene Ostracoda from outside the classic onshore sequences of SE England, and the present chapter primarily concerns that region. However, the occurrence of ostracods in offshore basins is briefly reviewed below.