The vice-world champion. Duh.
Who becomes the World Champion if the current world champion dies?

I imagine that if he died while the candidates tournament/matches (whichever system was in vogue at the time) determined a challenger, similar to Fischer insanely not playing Karpov, the challenger would be it. Otherwise, the top two of the next candidates tournaments/matched would play for the title.
They would hire some top detective to solve the mystery of the murder of the chess world champion and if the detective successfully does that, then the detective will be the new world champion.
Of course the twist will be that the detective would already know this, so he would be the one who killed the world champion and framed the wrong guy convincingly enough to fool the whole world, so as to become the world champion of chess.

there've been 2 instances when the world champion has forfeited. First is when Bobby Fischer refused to play against Karpov, so Karpov was made WC. So, back then the rules were that the challenger would be the WC. The second instance was when Kasparov split from FIDE and formed the PCA. In that situation, Karpov was the FIDE WC as he was the previous WC. But going by the previous rule, the challenger was to be the next WC. At that time, the challenger was Nigel Short and Nigel Short also decided to break away from FIDE and play under the PCA. So, since the World Champion and the challenger both decided to break away from FIDE, they made the previous World Champion as the current World Champion, i.e Karpov. So, I think from this we can infer that if the World Champion dies or refuses to defend the title, then the challenger will be the next WC. So, now if Magnus Carlsen were to die, I'm guessing that Fabiano Caruana will the next WC

there've been 2 instances when the world champion has forfeited. First is when Bobby Fischer refused to play against Karpov, so Karpov was made WC. So, back then the rules were that the challenger would be the WC. The second instance was when Kasparov split from FIDE and formed the PCA. In that situation, Karpov was the FIDE WC as he was the previous WC. But going by the previous rule, the challenger was to be the next WC. At that time, the challenger was Nigel Short and Nigel Short also decided to break away from FIDE and play under the PCA. So, since the World Champion and the challenger both decided to break away from FIDE, they made the previous World Champion as the current World Champion, i.e Karpov. So, I think from this we can infer that if the World Champion dies or refuses to defend the title, then the challenger will be the next WC.
I know this thread is two years old, but isn't this claim (which has been said a couple of times in the thread) mistaken? I don't believe Karpov became Fide world champion by virtue of his title before 1985. Rather, unless my memory is worse than I thought, he won it because Fide had the top two remaining participants in that cycle's candidates' matches -- Karpov and Timman -- play a match to determine the championship, and Karpov won that match.
The chessplayer who killed him would become the new world champ, but not for long, because somebody would depose him in the same way.
LMAOOOO
there've been 2 instances when the world champion has forfeited. First is when Bobby Fischer refused to play against Karpov, so Karpov was made WC. So, back then the rules were that the challenger would be the WC. The second instance was when Kasparov split from FIDE and formed the PCA. In that situation, Karpov was the FIDE WC as he was the previous WC. But going by the previous rule, the challenger was to be the next WC. At that time, the challenger was Nigel Short and Nigel Short also decided to break away from FIDE and play under the PCA. So, since the World Champion and the challenger both decided to break away from FIDE, they made the previous World Champion as the current World Champion, i.e Karpov. So, I think from this we can infer that if the World Champion dies or refuses to defend the title, then the challenger will be the next WC.
I know this thread is two years old, but isn't this claim (which has been said a couple of times in the thread) mistaken? I don't believe Karpov became Fide world champion by virtue of his title before 1985. Rather, unless my memory is worse than I thought, he won it because Fide had the top two remaining participants in that cycle's candidates' matches -- Karpov and Timman -- play a match to determine the championship, and Karpov won that match.
You are right, even if it for some reason often is claimed that Karpov was declared World Champion. If someone should have been declared World Champion it should have been Timman, who had lost the Candidates final to Short, but FIDE preferred to hold a title match between him and Karpov, who had lost in the Candidates semi. Given the circumstances they probably considered just handing the title to Timman (ranked #34 in the world) as making the title even less competitive.
If the WC were to die (or simply retire) before the candidates tournament, then it seems obvious that the candidates tournament would become the world championships. I'm curious what would happen if he died after the candidates tournament. It would seem that the winner of the candidates tournament would become WC, but what are the actual rules that determine this?