Dundanion Castle, Tudor tower house in Blackrock, Ireland

Dundanion Castle is a ruined limestone tower house of about 1564 in Blackrock, built by the Galwey family. It stands on the private grounds of Dundanion House, designed by Sir Thomas Deane in the 1830s, and is partly visible from the old Cork, Blackrock and Passage Railway walkway and Holland Park.

The castle was built around 1564 by the Galwey family and appears on the late 16th-century Pacata Hibernia map as 'Galwaies castle'. It represents early colonial settlement patterns in this area of Cork.

The name Dún Daingean means 'firm fortress' in Irish, while the earlier name Galwey's Castle recalls the family that built the tower house around 1564. The ruin stands on the private grounds of Dundanion House, so it is seen from the old railway walkway and nearby Holland Park rather than visited.

The castle is partly visible from the old Cork, Blackrock and Passage Railway walkway, but it sits on private property. Visitors can view the exterior structure only from public vantage points without entering the grounds.

The adjoining slipway shows the castle once stood at the River Lee waterfront, before later land reclamation left it inland. Some sources name this slipway as William Penn's departure point on a voyage to the Americas before Pennsylvania was founded in the 1680s.