Quercus petraea (syn. Quercus sessiliflora), the sessile oak, also known as the Irish oak. It is sometimes also called the Welsh oak, Cornish oak or Durmast oak, is a species of oak tree native to most of Europe, into Anatolia and Iran.

The sessile oak is the official national tree of Ireland, (where it is known as the Irish oak or Dair ghaelach). Similarly, it is an unofficial emblem in Wales (where it is called Welsh oak) and Cornwall (where it is referred to as the Cornish oak).