Viacheslav Vasilyevich Ragozin (Russian: Вячесла́в Васи́льевич Раго́зин; 8 October 1908 – 11 March 1962) was a Soviet chess player, writer and editor.

At the very strong Moscow tournament of 1936, he beat Salo Flohr and Emanuel Lasker and came very close to defeating José Raúl Capablanca, the ever-resourceful ex-world champion scrambling to find a draw by perpetual check at the game's frantic conclusion.

He recognized that Ragozin would make an ideal sparring partner and they played many secret training matches, as Botvinnik prepared for important world championship encounters.

As Botvinnik was attempting to put together a repertoire of solid, reliable openings, it was vital that they were rigorously tested against any latent sacrificial play.

His contributions to opening theory mainly concerned the development of systems by which Black could achieve equality in the Queen's Gambit and Nimzo-Indian complexes.

The Queen's Gambit Declined Ragozin Defence, typically arrived at via the moves 1.d4 d5 2.c4 e6 3.Nf3 Nf6 4.Nc3 Bb4 (or by transposition) offering Black active play from the start, has enjoyed a resurgence in recent times.