William Kelly (22 August, 1811 - 11 February, 1888), born in Pittsburgh, Pennsylvania, was an American inventor. Kelly studied metallurgy at the Western University of Pennsylvania. Instead of getting a job as a scientist, Kelly, his brother, and his brother-in-law started a a dry goods and commission business, which they called McShane & Kelly. After a fire destroyed their warehouse, William and his brother John decided to move to Eddyville, Pennsylvania in 1847 to enter the iron industry.
In 1846, they purchased an iron manufacturing company in Lyon county on the Cumberland river, called Eddyville iron-work. They renamed the factory to Kelly & Company.
"Kelly's air-boiling process," a process for the manufacture of boiler-plates, was invented by Kelly before Henry Bessemer, the scientist credited with the invention, patented the same technique.