Hermann August Hagen (30 May 1817 – 9 November 1893) was a German entomologist who specialised in Neuroptera and Odonata.
He had established himself as one of Europe's preeminent entomologists by 1867 when he accepted a position at Harvard University to curate the Museum of Comparative Zoology.
In 1870 he became the first entomologist in the United States to hold the formal title, Professor of Entomology.