Itzehoe is a town of Germany, in the Bundesland of Schleswig-Holstein, the capital of Kreis Steinburg.

It is located on the Stör, a navigable tributary of the Elbe, 51 km northwest of Hamburg and 24 km north of Glückstadt. The population is 33,549.

The church of St Lawrence, dating from the 12th century, and the building in which the Holstein estates formerly met, are noteworthy. The town has a convent founded in 1256, a high school, a hospital and other benevolent institutions. Itzehoe is a busy commercial place. Its sugar refineries are among the largest in Germany. Ironfounding, shipbuilding and wool-spinning are also established industries in the town, and manufactures include machinery, tobacco, fishing-nets, chicory, soap, cement and beer. Fishing employs some of the inhabitants, and the markets for cattle and horses are important. A considerable trade is carried on in agricultural products and wood, chiefly with Hamburg and Altona.

Itzehoe is the oldest town in Holstein. Its nucleus was a castle, built in 809 by Egbert, one of Charlemagne's counts, against the Danes. The community which sprang up around it was variously called Esseveldoburg, Eselsfleth and Ezeho. In 1201 the town was destroyed, but it was restored in 1224. The new town was granted the Lübeck rights by Adolphus IV in 1238, and the old town in 1303. During the Thirty Years War Itzehoe was twice destroyed by the Swedes, in 1644 and 1657, but was rebuilt on each occasion. It passed to Prussia in 1867, with the duchy of Schleswig-Holstein.

Germany's lowest elevation is to be found a short distance from Itzehoe, in the Wilstermarsch, which reaches 3.54 m below sea level.