Burg Arlen, Medieval castle in Tyrol, Austria.

Burg Arlen is a medieval castle ruin in the Tyrolean Alps near Sankt Anton am Arlberg. The remains show stone foundations and structural elements that reveal how this mountain fortress was originally laid out for defense.

The castle was built in medieval times as a fortified stronghold to control the Arlberg pass. Over the centuries it fell into disrepair and survives today mainly as a ruin.

The name Arlen survives in the hamlet of Nasserein and the Schloßkopf hill above it. Since the late 19th century a Lourdes chapel has stood on the castle hill; its corner stones are reused bossed ashlars from the castle. The site has belonged to the Alber family since the mid-19th century.

The ruin sits on the Schloßkopf, a low knoll above Nasserein east of St. Anton. The site is reached on foot; the remains are limited to a 2.15 m thick stretch of wall and part of the ring-wall footing. The Lourdes chapel built at the end of the 19th century stands on the hill, using former bossed stones from the castle as corner blocks.

The castle hill was partly destroyed in 1974 during preparations for a planned coffee house; a 2.15 m thick wall fragment survives and is read as the east wall of the bergfried, a square tower about 10.5 m on each side. A Lourdes chapel built there in the late 19th century has corner stones made of former bossed ashlars from the castle.