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- Timothy Hackworth (1786–1850) - Early steam locomotive designer, associate of William Hedley and George Stephenson
- James Harrison (1816–1893) - Pioneer in the field of mechanical refrigeration
- Beulah Louise Henry (1887–1973) - Nicknamed "Lady Edison", patents included bobbin-free sewing machine and vacuum ice cream freezer
- William Hedley (1779–1843) - Railway pioneer, built the first practical steam locomotive relying only on the adhesion of wheels to rails
- Hero of Alexandria (c. 10–70 AD) - Described many inventions including the aeolipile and the windwheel
- August Horch (1868–1951) - Automotive engineer, founder of Audi
- Jonathan Hornblower (1753–1815) - Steam power pioneer, developed early compound engine
- Elias Howe (1819–1867) - Refining Hunt's ideas, granted first U.S. patent for a sewing machine using a lockstitch design
Read more about this topic: List Of Mechanical Engineers