Henry Louis Langhaar (October 14, 1909 – September 28, 1992) was a mathematician, engineer, researcher, educator, and author in the field of engineering mechanics.
In 1978, he retired as Professor Emeritus, after 31 years in the Department of Theoretical & Applied Mechanics (TAM) at the University of Illinois at Urbana-Champaign.
His interests spanned fluid and solid mechanics, and specific research areas included aircraft structures, plates and shells, and buckling theory.