Alexander Stewart (1699 or 1700 – 2 April 1781) was an Irish landowner who grew rich by inheriting a fortune from Robert Cowan, a former governor of Bombay.

[6] Alexander's grandfather is not known by name, but Alexander was a great-grandson of Charles Stewart, whose father John[7][8] was given land at Ballylawn in County Donegal in the plantation of Ulster, built Ballylawn Castle on that land, and held fishing rights in Lough Swilly.

[17] During his residence in Belfast he became a convinced Whig, in line with the general reformist sentiment of the Presbyterian town.

Being now rich, Stewart retired from business in 1743, and used the money from the Cowan inheritance to become a substantial landowner in County Down by buying estates at Comber and Newtownards in 1744.

[34][35] The Stewart family papers are preserved in the Public Record Office of Northern Ireland.