Sir Mark John MacTaggart-Stewart, 1st Baronet (12 October 1834 – 26 September 1923), known as Mark John Stewart until 1880, was a Scottish Tory Member of Parliament in the House of Commons of the United Kingdom. He represented Wigtown Burghs from 1874–80 and again for a few months later in 1880 and also sat for Kirkcudbrightshire between 1885 and 1906 and briefly in 1910.
In 1880 he assumed the additional surname of MacTaggart. On 7 October 1892, he was made a Baronet, of Southwick in the Stewartry of Kirkcudbright and Blairderry in the County of Wigtown. MacTaggart-Stewart died in September 1923, aged 88. He was succeeded in the Baronetcy by his only surviving son, Sir Edward Orde MacTaggart-Stewart, 2nd Baronet.