Bois-Seigneur-Isaac Castle, Heritage castle in Braine-l'Alleud, Belgium.

Bois-Seigneur-Isaac is a stately home in Ophain-Bois-Seigneur-Isaac, part of Braine-l'Alleud in Walloon Brabant. The present building dates from 1737. Its long cream-coloured facade has a dark slate roof and three sections; the taller central one carries a rounded pediment with a small circular clock or window, three tall arched windows below and three arched windows above. Only foundations and one tower of the original fortress remain.

The site was built in the early 12th century by the descendants of Isaac de Cambrai, and only the foundations and one tower of that first fortress remain. In 1737 the stronghold was turned into a pleasure house, which is the building seen today. It is listed as exceptional heritage of Wallonia and belongs to the Snoy family.

The castle belongs to the Snoy family and is listed as exceptional heritage of Wallonia. The diplomat Jean-Charles Snoy et d'Oppuers (1907–91), a resident of the château, is its best-known figure.

Visiting requires advance planning since access is limited to specific occasions throughout the year. It is best to arrange a group visit in advance and familiarize yourself with the approach roads beforehand, as this is a private residence with scheduled access times.

The 1737 rebuilding kept only the foundations and one tower of the original 12th-century fortress, so a defensive remnant survives within the pleasure house. The château is listed as exceptional heritage of Wallonia and remains in the hands of the Snoy family.