Sunnyside Royal Hospital was a psychiatric hospital located in Hillside, north of Montrose, Scotland. The hospital was founded in 1781 by Susan Carnegie as the Montrose Lunatic Asylum, Infirmary & Dispensary and obtained a Royal Charter in 1810. The original building was situated on the Montrose Links on a site bounded by Barrack Road, Ferry Road and Garrison Road.
In 1834, the Governors of the asylum, carrying out the wishes of Mrs Carnegie (who had strongly advocated the appointment of a medical specialist in insanity) appointed the phrenologist William A.F. Browne as medical superintendent. Browne was to prove an inspired choice and an energetic and resourceful leader. He regarded public education as part of his duties, and gave a series of lectures which became enormously popular and influential. In 1837, five lectures were published together under the title What Asylums Were, Are and Ought To Be; this book came to the attention of the Dumfries philanthropist Elizabeth Crichton. She travelled to Montrose, interviewed Browne and offered him the equivalent post at the Crichton Royal in Dumfries. Crichton offered Browne a raise from £150 to £350 per annum. Browne was succeeded at Montrose by Richard Poole, an early psychiatric historian, and, later, by Dr James Howden, who identified cases of pellagra in the asylum.
In 1858, a new improved asylum was completed to the north of Montrose in the village of Hillside on lands of the farm of Sunnyside and the old site was vacated. This site was further developed with the construction of a new facility for private patients called Carnegie House in 1899. Despite this addition, overcrowding was a problem, as the asylum's patient numbers had grown to 670 by 1900. This situation required additional building work to be undertaken. Consequently, two new buildings - Howden Villa (1901) and Northesk Villa (1904)- were added to the facility. Additional staff were required to care for the additional patients and the Westmount Cottages were built in 1905 to house them. In 1911 the lease of Sunnyside Farm finally expired and over 52 acres were purchased for the sum of £4500. A further development was the addition of Angus House, which was built in 1939 to accommodate elderly patients suffering from dementia.