A zero-sum game is any interaction where one person's gain results in an equivalent loss by another participant. The concept of a zero-sum game is prominent in game theory. Chess is an example of a zero-sum game, in which one person wins at the expense of another.

Some transactions in the financial market are zero-sum games. Trading in options and futures are common examples: Every contract is an agreement between two parties, where one party wins and the other party loses.

In financial markets, there may be millions of participants in a zero-sum game. Assets can be bought and sold among millions of investors, redistributing wealth but not increasing the total.