A cycle, in general, is a sequence of events or developments that repeat over time. In stock markets, a market cycle constitutes the longer-term price movements in a broader market index (e.g., a complete uptrend and a complete downtrend). A market cycle initiates from the highest high or lowest low for a given time and is considered over when the prices of the index head for the initial point. Market cycles, like price trends, can be of a long, short, or intermediate length.

There are two common stock market cycles: cyclical cycles and secular cycles. Market cycles can also be classified as bear market cycles and bull market cycles.