Fort van Oelegem, Military fortress in Oelegem, Belgium

Fort van Oelegem is a first-order fort of the Antwerp outer line, built of unreinforced concrete on a trapezoidal plan of about 20 hectares, ringed by a 40–50 m wide moat. Its weathered grey facade has a tall round-arched entrance flanked by two recessed niches with small square openings, and a flat roof slab with a low railing along the base.

The fort's construction was assigned on 27 February 1909 as part of the Hoofdweerstandstelling, the main resistance line of the Antwerp fortress belt, and was to be finished by 1 July 1912. At the start of the First World War it was still far from operational and had no ammunition. It fired its first shots on 5 October 1914 at Fort Kessel and surrendered with Antwerp on 10 October 1914.

The fort represents a style of Belgian military architecture from the early 1900s. Visitors can observe how such structures were designed and built to defend territory.

The fort is open on some days in summer, on bat evenings and by appointment; the annual open day falls on the last Sunday of April. The site is managed by the WGFO working group of Natuur2000. Visits are guided, and the grounds are uneven.

Since 2014 Fort van Oelegem has been the largest bat hibernation reserve in Flanders. Counts in early 2019 recorded about 1,500 bats of around ten species, and for the fringe-tailed bat (franjestaart) it has long been the most important wintering site. The fort is privately owned and managed by the WGFO working group of Natuur2000.