Sergei Mosin was a Russian military officer and firearms designer, best known for creating the Mosin–Nagant rifle. Born in 1849, he played a significant role in the development of this bolt-action rifle, which became the standard infantry weapon for the Imperial Russian Army and was widely used during both World Wars. The Mosin–Nagant rifle was praised for its accuracy and reliability, making it a favored choice among soldiers. Mosin's contributions to firearms design have had a lasting impact, and his work continues to be studied by military historians and firearms enthusiasts today.