Thomas S. Sinclair (c. 1805 - 1881) was an American lithographer. Born in the Orkney Islands, Scotland, Sinclair studied lithography in Edinburgh and other European cities before moving to the United States sometime before 1833. He was established in Philadelphia by 1833, when he drew a dancing scene for the firm of Kennedy and Lucas, which went out of business that same year. In 1838, Sinclair acquired the press of John Collins and opened his own lithography firm. He was among the first lithographers in Philadelphia to experiment with color lithography, beginning in 1843. By 1848, his skills ad advanced to such a degree that he won a silver medal for color lithography at the Franklin Institute's exhibition. Sinclair's brother, William B. Sinclair, joined the firm in 1854, and from that year until 1859 the establishment was known as Thomas Sinclair and Company. His son joined the company at one point also, and then the firm's name changed to Thomas Sinclair and Son. Sinclair died in Philadelphia in 1881.