The statistics of extreme wave heights is of great importance in many ocean and coastal engineering applications and is an important part of physical oceanography. For example, in the design and operation of marine structures one needs to take the influence of extreme ocean environments into account and estimates of very large return values of wave heights are often needed. However, due to the limited length of time series of wave measurements, reliable estimates of high return values are difficult to obtain, and the uncertainties are large. This paper presents a regional frequency analysis of extreme significant wave height over the North Atlantic ocean in a changing climate. Regional Frequency Analysis (RFA) is a well established methodology for extreme value analysis in various geosciences, and has been particularly promoted within hydrology and flood frequency analysis. However, RFA has not been used as extensively in ocean sciences, and only a few applications on marine events are reported in the literature. This study demonstrates, however, that regional frequency is well suited for spatial extreme value analysis of wave- and other met-ocean parameters.