Grönsö Castle, Renaissance castle in Enköping Municipality, Sweden.

Grönsö Castle is a manor house on the island of Grönsö by the Grönsö Sound in Lake Mälaren, Enköping Municipality. The main building was raised in 1607–1611 for Johan Skytte in grey stone and brick, possibly after French models, with a tower-crowned roof and four rectangular corner towers. Repaired in the 1730s, it lost its towers and received smooth plastered façades under a hipped roof.

The castle was built between 1607 and 1611 by Johan Skytte, a powerful figure at the Swedish royal court who served as tutor to the young King Gustav Adolf. It was constructed during a period when Sweden was growing into a major European power.

The painted ceilings and interiors from the 17th century show the artistic choices of Swedish nobility at the time. Walking through the rooms gives a direct sense of how a grand Swedish household looked and felt during that era.

The park is open to the public, while the castle interior can be visited on guided tours during the summer months. The estate lies on the island of Grönsö by the Grönsösund strait, and the medieval Utö hus is visible from the park.

The estate is home to Sweden's oldest commercial apple orchard, planted in 1623, which still produces fruit and juice today. Visitors can buy products from this orchard directly on site.