A stage (55.8–48.6 Ma ago) in the Eocene epoch, preceded by the Thanetian (Palaeocene) and followed by the Lutetian, named after the Ypres Clay, Belgium. It is roughly contemporaneous with the Penutian and lower Ulatisian (N. America), upper Waipawan, Mangaorapan and lower Heretaungan (New Zealand), and the lower Johannian (Australia).