Ooidonk Castle (Dutch: Kasteel Ooidonk) is a castle in the city of Deinze, East Flanders, Belgium. The castle is the residence of the current Count t'Kint de Roodenbeke. Ooidonk Castle is situated at an altitude of 11 meters.
Ooidonk is already mentioned in 1230 : "Nicolas, chaplain of Hodunc".
The castle was destroyed for the first time in 1491 by the people of Ghent in revolt against Maximilian of Austria.
The ruins and lands were later acquired by Martin della Faille, a notable merchant from Antwerp. He rebuilt the castle in a Renaissance style and transformed it into a place of residence in Hispano-Flemish style.
In 1944, the castle was classified as a protected landmark. In 1980, other constructions around it were also classified, and in 1995, so was the rest of the estate. Ooidonk Castle is open to the public from April 1 to September 15, and the park (with its French garden) can be visited year round.