Irish brewer and first lord mayor of Dublin under the reformed corporation (1851), whose brewery (Guinness PLC) became one of the largest in the world.

In 1855 Guinness assumed control of the brewing business, Arthur Guinness & Sons, started by his grandfather, Arthur Guinness (died 1803). He then developed a large export trade of stout to the United States, England, and continental Europe, which became the foundation of his fortune; he was said to be the richest man in Ireland. Among his many philanthropic activities was the restoration beginning in 1860 of St. Patrick's Cathedral, Dublin, which was in a state of near ruin, and the adjacent Marsh Library. He represented Dublin in Parliament from 1865 until his death. He was created a baronet in 1867.