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 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. After the French defeat in the Franco-Prussian War, Haguenau was ceded to the new German Empire. It was part of the German Empire for 48 years from 1871 to 1918, when at the end of World War I it was returned to France. This transfer was officially ratified in 1919 with the Treaty of Versailles.
Haguenau is a rapidly growing town, its population having increased from 22,944 inhabitants in 1968 to 34,504 inhabitants in 2017. Haguenau's urban area has grown from 40,375 inhabitants in 1968 to 59,796 inhabitants in 2017.