Elisabeth (Lis) Jacobsen, née Rubin, (1882–1961) was a Danish philologist, archaeologist and writer. She is remembered first and foremost for her research and publications on the history of the Danish language but she was also an expert runologist who published a comprehensive analysis of all known runic inscriptions in Denmark. From 1911, Jacobsen played a major role in all fields of research related to the Danish language.
Born on 29 January 1882 in Copenhagen, Jacobsen grew up in a rich Jewish family, the daughter of Marcus Rubin (1854–1923), director of the National Bank of Denmark, and his wife Kaja Davidsen (1854–1909). After matriculating from N. Zahle's School in 1900, she qualified as a schoolteacher in 1903. The same year she married the historian Jacob Peter Jacobsen. In 1904, she began to study Scandinavian philology at Copenhagen University where she was awarded the university's gold medal for her 1907 essay Naar og hvorledes har det fællesnordiske Sprog spaltet sig i forskellige Grene (When and how the common Nordic language broke up into different branches). After receiving her master's degree in 1908, in 1910 she became Denmark's first woman to earn a doctorate in Nordic philology with a thesis titled Studier til det danske Rigssprogs Historie fra Eriks Lov til Chr. III.s Bibel (Studies on the History of the Danish Language from Erik's Law to Christian III's Bible).
Realizing the limitations of further research into the Danish language owing to the absence of adequate texts and dictionaries, in 1911, thanks to the support of Kristian Erslev and Carl S. Petersen, she founded Det danske sprog- og litteraturselskab or DSL (Danish Society for Language and Literature) which she headed until 1931, whereafter she served as administrator. DSL gained importance through the publication of Jacobsen's numerous works.
In collaboration with Harald Juul-Jensen (1982–1949), Jacobsen organized the work of publishing a comprehensive Danish dictionary, Ordbog over det Danske Sprog which appeared in 28 volumes from 1919 to 1956. As a result of her interest in runes, thanks to the support of the Carlsberg Foundation and in collaboration with Erik Moltke, Danmarks Runeindskrifter (Denmark's Runic Incriptions) was published in 1942, covering descriptions, illustrations, a lexicon and an atlas with photographs.