The Château d'Altkirch was a castle, now destroyed, in the commune of Altkirch in the Haut-Rhin département of France.
[1] Situated on the edge of a spur overlooking the valley of the River Ill, the castle lost its strategic importance in the 16th century and slowly declined.
After 1659, the owners (Mazarin and his heirs) showed little interest in the structure and some external buildings were put aside (prison, keeper's house).
One part still exists - to the north, heavily modified during the 19th and 20th centuries, and called the "maison de guet" (watch house).
A chapel was part of the castle, dedicated to St Catherine and containing a 14th-century indulgence.