There used to be two competing world championships in Gi BJJ(Mundials and another one I can't remember the name of) but I think they merged now. Many weight classes multiplied by several belt classes, although people usually refer to the black belt class when talking about world champions without explicitly mentioning that they didn't compete at BB...then there's also the Absolute class, and sometimes Seniors for the over 40 crowd.
For instance Steve Maxwell, kettlebell guru is a multiple time BJJ world champion, but all of his wins came in the Old Geezers division(he started late in life) so he's not as well known as some others.
Then you also have ADCC which some people see as the de facto World championships of no-gi BJJ etc...
Now FILA is getting in on the game too with their Grappling ruleset and the first World Championships are just around the corner, so expect even moar world champions in the future
