Who is the oldest person to have won a world championship in any sport?
For this discussion, the sport must include some sort of specialized physical skill (so, for example, darts would qualify, but chess would not). It should be one played by at least hundreds of people in at least, say, a half-dozen countries. “World championship” implies that competitors from multiple countries came together to compete and decide a winner - but the competition need not necessarily have that title: the Olympics would qualify.
My Googling wasn’t much help: it mostly turned up lists of old champions in a limited number of well-known sports.
Oscar Swahn won a gold medal in a rifle competition at age 64 in the 1912 Olympics, and later won a silver in the 1920 Olympics at age 72, making him the oldest in both categories.
It’s hard to imagine anyone topping this - I can’t think of any other sport that does involve physical skill, but does not advantage strength or agility - just concentration and steadiness.
So far, everyone is answering your post by citing the person who was the oldest when they won; however, the above sentence can be read to be looking for someone born in 1935 who won Olympic gold in 1956 & is now 89 years old which would be a totally different answer. Which were you looking for?