| Jakob Johan Adolf Appellöf | |
| Birth Date: | 2 November 1857 |
| Birth Place: | Garda on Gotland, Sweden |
| Death Place: | Uppsala, Sweden |
| Fields: | Marine biology |
| Author Abbrev Zoo: | Appellöf |
| Patrons: | Bünsow (sawmill magnate) |
| Education: | Uppsala University (PhD 1886) |
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| Known For: | Contributions to knowledge of cephalopods |
| Awards: | Royal Swedish Academy of Sciences, Royal Society of Sciences in Uppsala |
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Jakob Johan Adolf Appellöf (Garda on Gotland 2 November 1857 – Uppsala 5 January 1921) was a Swedish marine zoologist.
Appellöf matriculated at Uppsala University in 1877, earned his PhD in 1886 and became a docent of zoology in 1887. In 1889 he received the position of conservator at the Museum of Bergen in Bergen, Norway. He was appointed professor of comparative anatomy in Uppsala in 1910. With a donation from the sawmill magnate Bünsow, Appellöf established the Klubban Biological Station of Uppsala University, a station for the study of marine biology located on the west coast of Sweden. In 1919 he was elected a member of the Royal Swedish Academy of Sciences and in 1920 of the Royal Society of Sciences in Uppsala.
He made several important contributions to the knowledge of cephalopods.