Læsø is the largest island in the North Sea bay of Kattegat, and is located 19 kilometres (12 mi) off the northeast coast of the Jutland Peninsula, the Danish mainland. Læsø is also the name of the municipality (Danish, kommune) on that island. The island is a location mentioned in several instances in Norse mythology, including as the dwelling of the sea jötunn Ægir and as a feasting place of the Norse gods, the Æsir.
Modern Danish Læsø is first attested in Old Norse as Hlésey, meaning "Isle of Hlér". According to the Prose Edda book Skáldskaparmál, Hlér is another name for the sea jötunn Ægir who, according to the same book, there held feasts for the gods.