Lengberg Castle is a medieval castle in Nikolsdorf, East Tyrol, Austria, about 13 kilometres east of Lienz. The castle was built by the earls of Lechsgemünde beginning in the late 12th century, and came under the control of the Archbishop of Salzburg in the 13th century.
During the 15th century, a second storey was added to the structure by Austrian noble Virgil von Graben from the Meinhardiner family. In 1485, the castle's chapel was completely rebuilt, and was consecrated by the Bishop of Caorle, Pietro Carlo, in October of that year. Both the addition of the second storey and the chapel construction were recorded by Paolo Santonino, an Italian humanist known for his travel diaries. The area was ceded to the Kingdom of Bavaria during the Napoleonic Wars and was returned to Austrian control after the Congress of Vienna.