Anatoly Illarionovich Shirshov (Анато́лий Илларио́нович Ширшо́в, 8 August 1921, Kolyvan, Novosibirsk Oblast – 28 February 1981, Novosibirsk) was a Soviet mathematician, known for his research on free Lie algebras. He proved the Shirshov–Witt theorem, which states that any Lie subalgebra of a free Lie algebra is itself a free Lie algebra.[1][2]