Lawyer and politician. The son of Robert Dundas (1658 - 1726), he was born into a long line of politicians and lawyers. Dundas studied at Utrecht University in the Netherlands and was called to the Bar in 1709.
He served as Member of Parliament for Midlothian but was dismissed following the Malt Tax controversy, which gave rise to riots in 1725. In 1737 he was appointed as a Lord of Session and became Lord President of Court of Session on the death of Duncan Forbes in 1748.
In 1726, Dundas commissioned William Adam (1689 - 1748) to design the new Arniston House.
Dundas was married twice, his first wife having died in 1734. He was succeeded as Lord Arniston by his son Robert (1713 - 87), but his fourth son, Henry Dundas, Viscount Melville (1742 - 1811), became the most powerful politician of his time in Scotland.