Vredenburg or Vredeborch was a 16th-century castle built by Habsburg emperor Charles V in the city of Utrecht in the Netherlands. Some remains of the castle, which stood for only 50 years, are still visible on what is now Vredenburg square in Utrecht. The Holy Roman Empire in 1528 annexed the Bishopric of Utrecht, and Emperor Charles V immediately ordered the construction of a castle in Utrecht, not only to protect the domain from invasion by the duke of Guelders, but also to retain control over the city's unruly population. Construction was begun in 1529 and completed in 1532.