Birger Jarls Tower, fortified tower on Riddarholmen, Stockholm, Sweden

Birger Jarls torn is a brick defensive tower on the northwest corner of Riddarholmen, 12.9 metres in diameter and 14.4 metres high to the cornice on the side facing Lake Mälaren. It has four storeys with timber floor structures, and its present roof dates from the 1750s. The tower now houses the offices of the Chancellor of Justice.

The tower was built around 1530 under King Gustav I of Sweden to replace earlier wooden fortifications destroyed by fire in 1525. Its construction was part of efforts to strengthen the city's defenses.

The name comes from a myth spread in the 18th century linking the tower to Birger Jarl, who lived about 300 years before it was built. The tower is not medieval: bricks of the same unusual format as those of St. Clare's Priory, demolished in 1527, show it was raised from that priory's material. Since 2007 it has housed the Office of the Chancellor of Justice.

The tower stands at the northwest corner of Riddarholmen, visible from Norra Riddarholmshamnen and the waterfront. Since 2007 it has housed the offices of the Chancellor of Justice, so the interior is not open to the public. Look for the round windows of the top-floor conference room and the white grouting added in 1589–1590.

The tower's name is a 17th-century myth: a 1917 study of its bricks showed they came from St. Clare's Priory, demolished in 1527, so the tower was built around 1530, not in Birger Jarl's 13th century. Look for the brick format shared with the priory.