Ekholmen Castle, Manor house in Enköping Municipality, Sweden

Ekholmen Castle is a manor house in Veckholm parish, south of Enköping near Norra Björkfjärden in Lake Mälaren. Its main building, erected 1736–48 to designs by Carl Hårleman, was rebuilt in 1857 under Fredrik Wilhelm Scholander with four corner towers and curved Baroque gables. The older wings, by Jean de la Vallée, survive from a house that burned in 1686.

The estate is first documented in 1369, when Bo Jonsson Grip exchanged it with Karl Ulfsson Sparre, whose family made it a seat farm. In 1571 Johan III granted Ekholmen to Pontus De la Gardie, whose heirs had Jean de la Vallée design a house with wings; that house burned in 1686. Erik Odelström built a new main building on the old foundations from 1736 to 1748 to designs by Carl Hårleman, and in 1857 Fredrik Wilhelm Scholander added four corner towers and Baroque curved gables.

The name Ekholmen means 'oak islet', after the estate's setting by Norra Björkfjärden. The wings visitors see today are the surviving parts of a house built for Pontus De la Gardie's heirs to designs by Jean de la Vallée, which burned in 1686; the main building was raised on its old foundations from 1736 to 1748.

The castle stands in Veckholm parish south of Enköping, by Norra Björkfjärden in Mälaren. The building is now divided into apartments, so visits concern the exterior; approach from the Enköping side and allow daylight for the facades and the water views.

Some of the older wings we see today originally belonged to a different house that burned down in 1686, which was designed by architect Jean de la Vallée. That earlier building had been created for the heirs of Pontus De la Gardie before the present construction took over the site.