Horatio Allen LL.D (May 10, 1802 – December 31, 1889) was an American civil engineer and inventor, and President of Erie Railroad in the year 1843–1844.
Born in Schenectady, New York, he graduated from Columbia University in 1823, and was appointed Chief Engineer of the Delaware and Hudson Canal Company (precursor to the railroad). In 1828 he was sent to England to buy locomotives for the canal company's projected railway. There he made the acquaintance of engineer George Stephenson. In 1829 he assembled the first steam locomotive to run in America, the Stourbridge Lion, which ran successfully at Honesdale, Pennsylvania.
From 1829 to 1834 he was the chief engineer of the South Carolina Canal and Rail Road Company, at that time the longest railway in the world (about 136 miles/218 km). He was the inventor of the so-called "swiveling truck" for railway cars. He wrote: The Railroad Era; First Five Years of its Development (1884).
In his other activities, from 1838 to 1842 he was principal assistant engineer of the Croton Aqueduct, the major water supply system for New York City; in 1842 he became connected with the New York Novelty Works, a major builder of marine steam and other engines; at various times chief engineer and president of the Erie Railway; consulting engineer for the Panama Railway and the Brooklyn Bridge; and in 1872 and 1873 was president of the American Society of Civil Engineers.