Bethlen castle in Sânmiclăuș, Alba, Renaissance castle in Sânmiclăuș, Romania.

Bethlen Castle is a square palace without an inner courtyard, its corners marked by tower-like volumes, built between 1668 and 1683 on a hill above the Kis-Küküllő valley. Its interior is divided into nine equal-sized rooms covered by Renaissance vaults with coloured stucco, and the doors and windows keep carved stone frames in Renaissance manner.

Miklós Bethlen (1642–1716) designed the castle himself, drawing on his studies in Utrecht and Leyden and on local building traditions. Construction ran from 1668 to 1683. In 1856 the estate passed to the Brukenthal family, who renovated the palace and turned it into an agricultural school; the family coat of arms is still visible.

The residence served the Bethlen family, who held considerable power in the region and shaped local affairs over generations. Today the building speaks to how nobility displayed their status through their choice of location and construction.

The castle stands on a hill northeast of Blaj, above the village of Sânmiclăuș in Alba County, and is reached on foot. The building is privately owned and currently unused, so there are no guided tours and the interior cannot be visited; the granary and park belong to the same ensemble.

Miklós Bethlen designed the castle himself after studying in Utrecht and Leiden, and the building was erected between 1668 and 1683. A defensive system of walls, five bastions and a water ditch was added in 1686–1689, but nothing of it survives today.