Burg Frenz, Medieval castle in Inden, Germany.

Burg Frenz is the remnant of a moated castle on the Inde in the Frenz district of Inden, North Rhine-Westphalia. The complex once stood on three islands: a main house with an old outer bailey, a square garden island to the north, and a 19th-century outer bailey with farmyard to the south. Only the southern outer bailey survives, now privately owned and inhabited by three families.

A 1104 charter names Harpern de Fragenzo as a witness, suggesting a fortified site held by a family of that name; the castle itself is first documented in 1226, when Heinrich IV von Limburg took it as a fief from Cologne. Through Ricarda von Frenz it passed to Kuno von Müllenark in 1324, and in 1361 Richard I von Merode redeemed the pledge, beginning over 450 years of Merode ownership.

The name Frenz comes from the noble family von Frenz, first documented in 1104 with Harpern de Fragenzo. The family bore the Limburg lion in its coat of arms. From 1361 the von Merode line held the castle for over 450 years, mostly residing at Châtelineau and visiting Frenz for hunting. Today three families live in the surviving southern outer bailey.

The site remains private property and viewing from outside is possible but entering the grounds needs the owner's permission beforehand. The location near the river provides easy identification when visiting the area, though careful approach is necessary out of respect for private land.

During repairs after a storm damaged a corner turret of the manor house in the early 1870s, 64 gold coins from various European states, minted between the 15th and 17th centuries, were found in the rubble.