Born in Dublin, he was the third son of the second Arthur Guinness (1768–1855), and his wife Anne Lee, and a grandson of the first Arthur (1725–1803), who had bought the St. James's Gate Brewery in 1759. He joined his father in the business in his late teens, without attending university, and from 1839 he took sole control within the family. From 1855, when his father died, Guinness had become the richest man in Ireland, having built up a huge export trade and by continually enlarging his brewery.