Sir Robert Abbott Hadfield, 1st Baronet FRS (28 November 1858 in Sheffield – 30 September 1940 in Surrey) was an English metallurgist, noted for his 1882 discovery of manganese steel, one of the first steel alloys. He also invented silicon steel, initially for mechanical properties (patents in 1886) which have made the alloy a material of choice for springs and some fine blades, though it has also become important in electrical applications for its magnetic behaviour.