Gustaf Johan Billberg (June 14, 1772 – November 26, 1844) was a Swedish botanist, zoologist and anatomist, although professionally and by training he was a lawyer and had science and biology as a hobby.
Billberg was the author of Ekonomisk botanik (1815-16), Enumeratio insectorum in museo (1820) and Synopsis Faunae Scandinaviae (1827).
He was elected member of the Royal Swedish Academy of Sciences in 1817.
The plant genus Billbergia was named for him.