This city is a port on both sides of the Kiel Fjord, an inlet of the western Baltic Sea, and lies at the eastern end of the Kiel Canal. The name Kyle, meaning fjord or spring, was used for the settlement as early as the 10th century. The city was founded in 1242, and it adopted the Laws of Lübeck, an agreement for the common defense of trade. It entered the Hanseatic League in 1284 and acquired additional trading privileges in the 14th century. In 1773 Kiel became part of Denmark, which ceded Norway to Sweden by the Treaty of Kiel in 1814. The city passed to Prussia in 1866 along with the rest of Schleswig-Holstein and became the capital of that province in 1917. After 1871 it also became an important naval base; it was the site of the German naval mutiny and a target of Allied bombing during World War II.

Kiel was largely destroyed in World War II but has since been rebuilt with extensive green spaces. Historic landmarks restored after 1945 include St. Nicholas Church and the palace of the dukes of Holstein-Gottorp, where the future Tsar Peter III of Russia was born. The Christian-Albrechts University of Kiel includes a renowned institute of world economics. An art gallery and botanical gardens, the oldest in Germany, are near the old university grounds. The city features shipping and ethnography museums, and the Institute of Marine Biology contains an aquarium. The annual Kieler Woche (Kiel Week) in June is an international regatta and cultural festival.