Thomas Harrison (1744 – 29 March 1829) was an architect and bridge engineer. He worked in northwest England, and many of his buildings were in Cheshire and Lancashire.
His most important project in Cheshire was the design of new buildings within the grounds of Chester Castle, a commission on which he worked from 1786 until 1815. He created accommodation for prisoners, law courts and a shire hall. His other works include public buildings, gentlemen's clubs, churches, houses and monuments. Most of his designs, particularly those at Chester Castle, were Neoclassical in design, and he was a major influence in the emergence of the Greek Revival in British architecture.
Harrison was also known for his innovative work on bridges. Skerton Bridge in Lancaster was the first substantial bridge in England to have a flat roadway, and Grosvenor Bridge in Chester, his final major commission, was the longest single-arched masonry bridge in the world at the time of its construction. He died at his home in Chester in 1829.