Monument prussien, Gothic Revival monument in Lasne, Belgium.

The Monument prussien is a Gothic Revival memorial about 6 m tall and weighing 3.5 tonnes, made of cast iron from the Royal Prussian Iron Foundry on a blue stone plinth and stepped base. Four gables with pinnacles and gilded finials surround the base of the spire, which ends in an Iron Cross bearing the date 1813, oak leaves, the initials FW and a small gilded crown. The south face carries gilded Gothic lettering under a laurel wreath.

The monument was erected in 1818 by the Prussians to plans by Karl Friedrich Schinkel, commemorating the roughly 6,700 Prussians who died at Waterloo and the action of Marshal Blücher's troops. It marks Plancenoit, the strategically important village taken by Bülow von Dennewitz's IV Corps after heavy fighting, which left Napoleon's position untenable. French soldiers damaged the cross in 1832; Marshal Gérard had it restored and an iron grille was added. It was restored in 1832, 1944, 1965 and 1997.

The gilded inscription on the south face reads "Die gefallenen Helden ehrt dankbar König und Vaterland. Sie ruhn in Frieden. Belle-Alliance den 18. Juni 1815." The Prussians called Waterloo the Battle of Belle-Alliance, and the name stuck on this memorial. The iron cross above repeats the 1813 decoration instituted by Frederick William III, with his initials FW, oak leaves and a small gilded crown.

The monument stands along the chemin de Camuselle, about 400 m north of Saint Catherine's church in Plancenoit, in the Lasne municipality of Walloon Brabant. It is reached on foot from the village; an iron fence runs in front of the plinth. The stele, base, steps and ironwork have been listed as a monument since 12 October 1981.

French soldiers damaged the cross in 1832, but Marshal Gérard, who had fought against Prussians at Wavre, ordered its restoration. The protective iron railings installed afterward remain a testament to this complicated later chapter in the monument's story.