The sea-level change around the coast of Ireland and the Irish Sea for the past 20 000 years is primarily the combined result of the glacio-isostatic adjustment of the crust to the removal of ice over the British Isles and the total eustatic change from the global ice sheets. However, the isostatic effects due to the removal of ice from northern Europe and North America and the addition of meltwater into the oceans also make a significant contribution. Predictions of sea-level change, based on glacio-hydro-isostatic models are compared with observations to constrain the ice volume over Ireland at the time of the last glacial maximum and the maximum ice height appears to have been of the order of 600 m. The models predict well the spatial variability in sea-level change observed across the region for Holocene and Lateglacial time, with levels above present being predicted only for northeastern Ireland and north of about Morecambe Bay. The models do not support suggestions that Lateglacial levels along the east coast of Ireland or the coast of Wales were 50–150 m above their present levels. Consistent models that would produce such large Lateglacial highstands are incompatible with all other sea level and glacial evidence for the British Isles. Palaeobathymetry and palaeoshoreline reconstructions for the Irish Sea indicates that a tenuous landbridge between Britain and Ireland developed only across the Celtic Sea, between about 18000 and 14000 years bp.