Sigurd F. Varian (1901-1961) was co-inventor of the klystron tube with his brother Russell Varian and William Hansen and co-founder of Varian Associates Company together with his brother Russell.

He was born in Syracuse, NY., on May 4 1901. He was the younger brother of famous Russell H. Varian. The Varian brothers belonged to a close-knit family, and the history of the brothers is so intertwined that is difficult to separate the two. From childhood, Russell could solve complex math problems in his head and dream-up inventions while watching someone make bread. Sigurd was the opposite, adventurous, practical and instantly handy with his hands. Theirs was a poor family and their father, John, believed that someday one of Russell’s inventions would save them all. Sigurd shared the dream but with one proviso: if Russell would ever conjure-up a family-saving invention, Sigurd would be there to build it. At the depth of the Great Depression, when jobs were the only thing harder to find than money, Sigurd predicted, “The way to be independent is to cash in on one of Russell’s ideas.” He was right. All it would take would be faith, persistence and time.

Teamed with his brother, Sigurd F. Varian took the lead in building practical models embodying Russell's ideas. During the Great Depression, Stanford University made lab space available to the Varians and later reaped a share of the royalties from their first big invention, the klystron tube.