Haguenau is a commune in the Bas-Rhin department of France, of which it is a sub-prefecture. It is second in size in the Bas-Rhin only to Strasbourg, some 30 km (19 mi) to the south. To the north of the town, the Forest of Haguenau is the largest undivided forest in France.
Haguenau was founded by German dukes and has swapped back and forth several times between Germany and France over the centuries, with its spelling altering between "Hagenau" and "Haguenau" by the turn. It was last German at the end of World War I, then briefly part of the independent Republic of Alsace-Lorraine before being annexed by France in 1919.
Haguenau is a rapidly growing town, its population having increased from 22,644 inhabitants in 1968 to 34,891 inhabitants in 2006. Haguenau's metropolitan area has grown from 43,904 inhabitants in 1968 to 64,562 inhabitants in 2006.