Tavastia Castle or Häme Castle is a medieval castle in Tavastia Proper, Finland. It is located in Hämeenlinna, the city between Helsinki and Tampere. Originally located on an island, the castle now sits on the coast of lake Vanajavesi. The castle consists of a central keep and surrounding curtain walls, enclosed by a moat. The keep originally had five turrets, but only two are apparent today. The curtain wall has a gatehouse, battlements, an octagonal brick corner turret, and a round gun turret. The lower tiers of the keep and curtain wall are of masoned granite and the upper tiers are red brickwork.

Although the exact date is disputed, the castle is generally considered to have been constructed in the 13th century. In addition to its status as a military fortress and home for Swedish nobility, the castle has seen use as a prison, and is currently a museum operated by the Finnish National Board of Antiquities. The castle is one of the main tourist attractions of southern Finland, being the centerpiece of the city and a popular venue for events, including renaissance fairs.