Burg Illingen, Castle ruin in Illingen, Germany.

Burg Illingen, also known as Burg Kerpen, lies in the valley of the Ill river in the centre of Illingen. Only parts of the main castle remain: sections of the perimeter walls and two towers, including a round tower at the south-east corner restored in 1951, whose ground floor holds a small late-Gothic chapel. The gatehouse of the outer bailey, built in 1605, is reached by a small stone bridge over the Ill.

Burg Kerpen is first documented in 1359, when Dietrich V. von Kerpen declared he held the castle at "Ildingen" as a fief from the Counts of Saarwerden; it likely predates that charter. Around 1620 an outer bailey completed its greatest extent. Burned by French troops in 1677, it was rebuilt into the 18th century, sold in 1830 and quarried for stone before Illingen bought it around 1900.

The castle grounds are open to the public as a leisure area owned by the municipality of Illingen. Each July the Burg- und Weiherfest is held here, and concerts and events run by local clubs take place on the site. The restored outer bailey with its pentagonal tower now houses a hotel-restaurant built in 1999.

The main castle area is freely accessible; the owner of the remaining grounds is the municipality of Illingen. The gatehouse, the small stone bridge over the Ill and the five-sided corner tower can be viewed from outside. The former tithe barn stands apart, separated by a road on an embankment, and is a private residence.

The castle's name is misleading: it is locally known as Burg Kerpen, after the von Kerpen family who held it as a fief from 1359. The round tower at the southeast corner of the main castle was restored in 1951 and has since become one of Illingen's landmarks; its ground floor holds a small late-Gothic castle chapel.