The Gann Fan is a technical analysis tool developed by the legendary trader W.D. Gann, which is used to identify key levels of support and resistance in price movements. It is a series of lines drawn at different angles, based on the price and time movements of a given market. The Gann Fan consists of a central line, which represents a major trend line, and a series of angled lines that are drawn at different degrees. These lines are then used to identify potential levels of support and resistance in a market.

The Gann Fan is based on the idea that markets move in specific geometric patterns, and that these patterns can be used to predict future price movements. The tool is particularly popular among traders who use technical analysis to identify trends and market reversals. It is commonly used in conjunction with other technical indicators, such as moving averages and oscillators, to confirm price movements and make trading decisions.