In some cases the champion has the right to refuse a challenge; in others, this results in forfeiting the title.
[1] While many competitive sports use some form of tournament to determine champions, a challenge match is the normal way of deciding professional boxing titles and the World Chess Championship.
Some racket sports clubs have a reigning champion who may be challenged by any other club member; a ladder tournament extends the challenge concept to all players, not just the reigning champion.
At elite-level competition, there is usually some governing body which authorises and regulates challenges, such as FIDE in chess.
The World Snooker Championship was contested via intermittent challenge matches between 1964 and 1968, when no commercial sponsor could be found for a scheduled tournament.