Linnep Castle, Medieval château in Ratingen, Germany.

Linnep Castle is a compact water castle in the Breitscheid district of Ratingen, its stone and brick wings rising behind a wide stone staircase that crosses the moat. The round tower with its pointed roof and sections of the ring wall date from the 12th century; the main building was rebuilt in 1769 and extended after 1855. A fortified outer courtyard with a gatehouse and outbuildings lies in front, and the Hummelsbach feeds the moat.

Linnep is first documented around 1090–1120 as 'linepo' in a Kaiserswerth abbey charter, and in 1093 a Wernherus de linepe appears in a Werden abbey deed. The knights of Linnep held the seat until 1461, when Eva von Linnep's marriage brought it to the counts of Limburg; from 1582 the Protestant Isselstein family lived here, buying it outright in 1643. In 1769 the old castle was rebuilt, keeping the roughly 1000-year-old round tower and ring wall; after 1855 further wings were added.

The castle chapel connection endures: Protestants gathered for worship inside the castle until 1684, when owner Vincent Schott von Isselstein gave land nearby for the Waldkirche Linnep, consecrated that year and one of the Rhineland's oldest Reformed churches. Since 2010 civil weddings have been held at the castle.

The castle is a private residence and can only be viewed from the outside. Access to the main building is via a wide staircase over the water-filled moat, and the forecourt is enclosed by a gatehouse with outbuildings. The reformed Waldkirche Linnep and the former castle mill stand about 100 metres to the south-west.

The moat is not dry: it is fed by the small Hummelsbach stream and partly widened into separate ponds, and three bridges cross it. The round tower with its pointed roof and stretches of the ring wall survive from the old castle and were folded into the 1769 rebuild.