Donald Watts Davies (June 7, 1924 - May 28, 2000) was a UK scientist who was a co-inventor of packet switching, along with Paul Baran and Leonard Kleinrock; he is the originator of the term "packet switching".

Just prior to Davies' death, he contested Kleinrock's views on the importance of Kleinrock's contributions.

Davies was born in Treorchy in the Rhondda Valley. He received BSc degrees in physics (1943) and mathematics (1947) at Imperial College in London. In 1955, he married Diane Burton.

See also: ARPANET