Herbert Girton Deignan (December 5, 1906 – March 15, 1968) was an American ornithologist who worked extensively on the birds of Thailand. Deignan was born in New Jersey, the son of Harry Francis and Anna Galena. He grew up in Pennsylvania and schooled in Mercersburg Academy before going to Princeton where he graduated with an Arts Baccalaureate in 1928. He became interested in birds early on and got in contact with Charles H Rogers, curator of the Princeton collections. He became interested in Thailand (Siam) and after graduating he took up a position in the Chiangmai college in northern Siam as a teacher of English. He stayed there from 1928 to 1932, collecting birds in the region that he sent back to Charles Rogers at Princeton.