William Delbert Gann (June 6, 1878 - June 18, 1955), also known as W. D. Gann, was a finance trader who developed the technical analysis tools known as Gann angles, Square of 9, Hexagon, Circle of 360. Gann market forecasting methods are based on geometry, astronomy and astrology, and ancient mathematics. He is the author of a number of books on trading, with his first book entitled Truth of The Stock Tape published in 1927.