Balquhain Castle is a ruined tower house in Aberdeenshire, Scotland. It served as the stronghold of the Leslies of Balquhain. The castle is located to the west of Inverurie, and is protected as a scheduled monument.
The castle was built in the 15th century on lands held by the Leslie family from 1340. On 5 July 1441, John Leslie of Balquhain made an indenture with four masons, David Hardgat, David Dun, Robert Masoun and Gilbert Masoun that they would complete his building work.
The castle was sacked during a feud with the Forbes family in 1526. The castle was rebuilt in 1530. On 1 September 1562, Mary Queen of Scots stayed at the castle. William Leslie, laird of Balquhain, was a leader of her vanguard at the Battle of Corrichie.
In March 1563, Queen Mary forgave William Leslie of Balquhain for his dealings with the George Gordon, 4th Earl of Huntly. She wrote to him to make provisions for her when she visited again in August 1564.
The place name was sometimes written as "Boquhane". In 1588, John Leslie, laird of Balquhain, was involved unsuccessfully in a fishing dispute, supporting the rights of Thomas Leslie of Banff against burgesses in Aberdeen. John Leslie's son fought with some men from Aberdeen and the families of the wounded men protested with bloody shirts or sarks. The dispute was settled by James VI and the Earl of Huntly.
John Leslie of Balquhain was married to Elspeth or Isobel Grant, a daughter of John Grant of Freuchie. John Leslie was accused of adultery with Janet Hunter in Aberdeen. He employed a nurse for his children called Bessie Roy. In 1590, she was involved in a trial for witchcraft and was acquitted. Among the accusations, it was said she had caused the death of a woman using a "plaid full of enchantments and sorcery".
The castle was burned by the forces of Prince William, Duke of Cumberland in 1746 and was abandoned.
The tower measures , and is surrounded by the remains of a barmkin.