Bornem Castle, Medieval castle and museum in Bornem, Belgium

Bornem Castle, also called Kasteel Marnix de Sainte-Aldegonde, is a neo-Gothic country house on the Oude Schelde, a cut-off arm of the Scheldt. Built in 1880 to plans by Hendrik Beyaert, it has grey stone walls, dark slate roofs, a tall round tower with a conical roof and a slender turret with a weathervane. A dark arched doorway sits at the base of the left tower, and small watch turrets in bluestone were added to the bridge in 1895.

A fortification against Viking raids stood here in the 10th or 11th century. In 1587 the war-damaged Land of Bornem was sold to the Spanish nobleman Pedro Coloma, who rebuilt the castle; its central keep was demolished in 1687. Count Ferdinand de Marnix had the remaining old walls pulled down in 1880 and commissioned architect Hendrik Beyaert to design the present neo-Gothic house, completed after Beyaert's death by Ernest Janlet, with small ashlar watchturrets added at the bridge in 1895.

The castle takes its name from the de Marnix de Sainte-Aldegonde family, owners since 1773, though Filips van Marnix van Sint-Aldegonde, possible author of the Wilhelmus, never lived here. The current count keeps the world's largest private collection of Pieter Bruegel the Elder engravings, 91 prints including The Big Fish Eat the Little Fish, shown inside the house.

The castle stands on the Oude Schelde in Bornem and can be visited only by appointment and on four Sundays in August and September. A visitor centre is housed in one of the outbuildings. The grounds are enclosed by a double moat, so the water is crossed by a bridge with small watchtowers added in 1895.

The estate borders the Vieil Escaut, a former watercourse of the Scheldt River that shifted its path centuries ago. This ancient bend in the river still shapes the landscape around the property today, revealing how natural forces have reshaped the land over time.