Gennady (or Gennadii or Gennadiy) Semenovich Makanin (1938–2017) was a Russian mathematician, awarded the 2010 I. M. Vinogradov Prize for a series of papers on the problem of algorithmically recognizing the solvability of arbitrary equations in free groups and semigroups.

His dissertation К проблеме тождества в конечно-определённых группах и полугруппах (On the identity problem in finitely-presented groups and semigroups) was supervised by Andrey Markov Jr. and Sergei Adian.

From the Steklov Institute of Mathematics he received in 1977 his Russian Doctor of Sciences degree (similar to habilitation) with dissertation Проблема разрешимости уравнений в свободной полугруппе (The problem of solvability of equations in a free semigroup).

Zlil Sela, Eliyahu Rips, and others have made important applications of Makanin-Razborov diagrams to geometric group theory.

In 1982 Makanin published a complete solution (an algorithm with proof of validity) to the problem of recognizing the solvability of equations in a free group.