The Hibernia Gravity Base Structure is the world's largest offshore oil platform, on the Hibernia oilfield south east of St. John’s, Newfoundland, Canada.
A 600 kilotonne gravity base structure (GBS) built after the Ocean Ranger disaster, it sits in 80 metres (44 fathoms) of water directly on the floor of the North Atlantic Ocean 315 kilometres (196 mi) off St. John's, Newfoundland at 46°45′1.57″N 48°46′58.54″W .
This GBS is the first offshore oil structure designed to resist iceberg forces, and supported a topsides weighing 39000 tonnes at towout, increasing to 58000 tonnes in operation. There were significant challenges faced by the engineering firms Doris Development Canada, Morrison Hershfield and Mobil Technology, in developing a structural solution with adequate strength which was also constructible. In addition, unusual design situations resulted from the construction methods and the structural components used.