William "Bill" Mason Gray (October 9, 1929 – April 16, 2016) was Emeritus Professor of Atmospheric Science at Colorado State University (CSU), and the head of the Tropical Meteorology Project at CSU's Department of Atmospheric Sciences. He was widely regarded as a pioneer in the science of forecasting hurricanes and one of the world's leading experts on tropical storms. After retiring as a faculty member at CSU in 2005, Gray remained actively involved in both climate change and tropical cyclone research until his death.