Hedeby (referred to also as Haithabu and latin Heidiba) was a settlement and trading center on the southern Baltic Sea coast of the Jutland Peninsula at the head of a narrow, navigable inlet, the Schlei in Schleswig-Holstein, northern Germany. The name means "the town on the heath". Haithabu was a Friesian settlement built around 770. It was surrounded on all land sides by an earthwork. In the 9th century a second settlement developed north and at the Haithabu creek inbetween. At the end of the 9th century the northern and southern part was abandoned for the central section. Later a nine meter (about 27 foot) high ring wall was erected.

It became a principal market because of its geographical location on the major trade routes between Germany and Scandinavia, and between the Baltic and the North Sea. Between 800 and 1000 the growing economic power of the Vikings who held it at this time led to its dramatic expansion as a major trading center. As Adam of Bremen reports, ships were sent from this portus maritimus to the Slavian areas, to Sweden, Samland (Semlant) and even Greece. It was the seat of a bishop and belonged to the archbishop of Hamburg and Bremen.

The town was sacked in 1050 by king Harold Hardrada of Norway during the course of a conflict with king Sweyn II of Denmark: a Norwegian skald, himself quoted by Snorri Sturluson, describes the sack as follows:

Burnt in anger from end to end was Hedeby [..]
High rose the flames from the houses when, before dawn, I stood upon the stronghold's arm

After Haithabu had been burned down by Harold, it was in 1066 plundered by Slavs. The inhabitants moved to Schleswig and Haithabu was abandoned.

See also: Birka, Wulfstan of Hedeby