David Thomas (1794-1882) was a Pennsylvania iron manufacturer who introduced into the United States the use of anthracite coal in the manufacture of pig iron.

Thomas was born on November 3, 1794, at Tyllwyd, Glamorganshire, Wales. He began working at the Neath Abbey iron works in 1812 and in 1817 was made general superintendent of the Yniscedwyn Iron Works, which was acquired by George Crane (1784-1846) in 1820. The two men conducted extensive experiments to use the local anthracite coal to smelt iron, but without success. In 1836 they learned of the hot-blast invented by James B. Neilson (1792-1865) in Scotland. Crane received a British patent for hot-blast smelting with anthracite on September 28, 1836, and a successful furnace was blown in at Yniscedwyn in February 1837.

In May 1837 the American engineer, Solomon White Roberts (1811-1882), visited the works as the agent for the Lehigh Coal & Navigation Company (LC&N) and the Philadelphia & Reading Railroad Company. Josiah White (1781-1850), Erskine Hazard (1790-1865), and others associated with the LC&N resolved to adopt the process in America, and Hazard went to Wales in 1838 and induced Thomas to emigrate. The Lehigh Crane Iron Company was incorporated in Pennsylvania on January 10, 1839. Thomas ordered most of the machinery for the new works in Britain before embarking for America in May 1839. The Crane Iron Works at Catasauqua, Pennsylvania, began production on July 4, 1840.

Although not the first to manufacture iron with anthracite coal in the United States, Thomas inaugurated the era of higher and larger furnaces and more powerful blast machinery. In 1854, Thomas, his sons, and other business associates organized the Thomas Iron Company across the Lehigh River in Hokendauqua, and Thomas resigned as superintendent of the Crane Company on July 1, 1856. He died in Catasauqua on June 20, 1882.