David Wayne Allan (born September 25, 1936) is an American atomic clock physicist and author of the Allan variance, also known as the two-sample variance, a measure of frequency stability in clocks, oscillators and other applications.

Allan was a consultant for the United Nations Development Programme in New Delhi in 1981 and a guest scientist in the People's Republic of China in 1982.

[5] Allan received the Silver Medal of the Department of Commerce in 1968 and one of the IR-100 awards of Industrial Research magazine in 1976.

[5] He received the Rabi Award of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society in 1984.

[4] In 2018 he received the Joseph F. Keithley Award in Instrumentation and Measurement of the Institute of Electrical and Electronics Engineers.