Henry Paul Hansen (April 28, 1907 – October 8, 1989) was an American palynologist known largely for his pioneering work on the vegetation history of the North American Pacific Northwest and for his time as the dean of Graduate Studies at Oregon State University from 1949 to 1972.

Hansen obtained the Bachelor of Science degree in 1930 from the University of Wisconsin–Madison, where he continued studying until he was awarded his M.Sc in 1931.

His research continued throughout his time there, including the collection and analysis of over 50 palynological records for the Pacific Northwest.

One of his seminal publications was Postglacial Forest Succession, Climate, and Chronology in the Pacific Northwest, published in 1947.

This work was all the more impressive given that chronologies at the time lacked stable age-depth controls later afforded by C14 dating.