John Rennie (1761 – 1821) was a Scottish civil engineer. He was the son of an East Lothian farmer, taking an interest in mechanical works at a young age. He matriculated from Edinburgh university which he left in 1783. After some years designing machinery, in particular using metal components where previously wood had been used, he set up his own business as a mechanical engineer in 1791. At this point, he moved into civil engineering firstly concerned with canals and their associated works. In 1797, he produced the designs for what is now Rudyard Lake as an additional feeder for the Caldon canal. He went on to design many bridges of which the best known are those across the Thames in London – Waterloo bridge, London Bridge and Southwark Bridge. He also designed or improved many docks and harbours including London’s East India and West India docks and Portsmouth, Devonport and Chatham dockyards as well as being accredited, along with Robert Stevenson, with the construction of the Bell Rock lighthouse.
He was elected to a fellowship of the Royal Society in 1798 and is buried in St. Paul’s Cathedral. Two of his sons, John and George, were also engineers of note.