The Waalian interglacial (German: Waal-Warmzeit or Waal-Interglazial) [1] or Waalian Stage was an interglacial period of the Early Pleistocene in north-west Europe. It was preceded by the Eburonian Stage and succeeded by the Menapian Stage. It coincides with part of the much longer Beestonian stage in Britain.[2] It is variously dated by different authorities. Oxford Reference gives 1.3 to 0.9 million years ago[3] and the British Geological Survey 1.6 to 1.36 million years ago.[2] However, the 2020 chart of the international authority on stratigraphic dating, the International Commission on Stratigraphy shows it as c. 1.6 to 1.4 million years ago.[4] It is distinct from other Pleistocene periods in its complexity, vegetational composition, and vegetational succession.
Its name is derived from a major branch of the Rhine delta, the Waal.