Peter Joseph William Debye ForMemRS was a Dutch-American physicist and physical chemist, and Nobel laureate in Chemistry.

Born Petrus Josephus Wilhelmus Debije in Maastricht, Netherlands, Debye enrolled in the Aachen University of Technology in 1901. In 1905, he completed his first degree in electrical engineering. He published his first paper, a mathematically elegant solution of a problem involving eddy currents, in 1907. At Aachen, he studied under the theoretical physicist Arnold Sommerfeld, who later claimed that his most important discovery was Peter Debye.

Peter Debye was described as a martinet when it came to scientific principles, yet he was always approachable and made time for his students. His personal philosophy emphasized a fulfillment of purpose and enjoyment in one's work. Debye was an avid trout fisherman and gardener, collector of cacti, and was "always known to enjoy a nice cigar".

In a 2010 publication Jurrie Reiding asserts that Debye may have been an MI6 spy. Reiding discovered that Debye was befriended by the well-documented spy Paul Rosbaud. They first met around 1930 when they were both working as editors for two scientific journals. They collaborated in the escape of Lise Meitner in 1938. According to Reiding, Debye was well connected in German scientific and industrial circles and could have provided MI6 with valuable information. For example, as board member of the German Academy for Aviation Research he was acquainted with Hermann Göring. Reiding also offers an explanation for Debye's hasty departure on 16 January 1940 for the United States: the date coincided with the planned (but later delayed) German invasion of the Netherlands a day later, information possibly provided to him by Rosbaud.