Lierna Castle, Medieval castle in Lierna, Italy.

Lierna Castle stands on a peninsula jutting into the eastern side of Lake Como, in the frazione of Castello in the comune of Lierna. It is not a single building but a group of connected buildings, the main portion built in the 10th century in Romanesque style over former Roman ruins. The 11th-century church of Saints Maurice and Lazarus is part of the complex, and the people of the frazione still occupy the castle.

The fortress was built in the 10th century on top of Roman foundations and became a focal point of rivalry between Milan and Como. These territorial disputes shaped its role until the early 1100s.

The church of Saints Maurice and Lazarus inside the castle walls has 15th-century frescoes. It was originally founded in Roman times and was designed to hold services during sieges, so its apse faces the lake as a protective bastion and its entrance lies within the castle walls.

The castle is not a single monument but the built-up frazione of Castello, the northwesternmost of Lierna's eleven hamlets, and its old walls are incorporated into the surrounding houses. Approach on foot through the lanes of the borgo; the church of Saints Maurice and Lazarus stands inside the former castle walls, with its apse turned toward the lake.

The castle is not a single building but a cluster of connected houses, and people still live in the frazione of Castello inside it. Its last military use came in the mid-16th century under Gian Giacomo Medici, called "Medeghino", a mercenary who used it as a naval base.