Andrey Nikolayevich Tikhonov (Russian: ?????´? ??????´???? ??´?????; October 17, 1906 – October 7, 1993) was a Soviet and Russian mathematician and geophysicist known for important contributions to topology, functional analysis, mathematical physics, and ill-posed problems.
He was also one of the inventors of the magnetotellurics method in geophysics.
Other transliterations of his surname include "Tychonoff", "Tychonov", "Tihonov", "Tichonov."