Kasparov, 15 games in a row.
For non-loss streak, it is Tal's 78 games.
This record of 20 consecutive wins is held by Bobby Fischer. (Some commentators give this as 19, electing not to count Fischer's game against Oscar Panno, who resigned after Fischer's first move as a protest). Fischer won his last seven games at the 1970 Palma de Mallorca Interzonal (including the one-move game against Panno). In the quarter-finals of the Candidates Matches leading to the world championship, Fischer swept Grandmaster Mark Taimanov 6–0. In the semi-finals, Fischer swept Grandmaster Bent Larsen by the same score. In the Candidates Match final, Fischer beat former World Champion Tigran Petrosian in the first game before Petrosian snapped the streak by beating Fischer in the second match game.[84]
Who has the biggest winning streak?