Maria Johanna Dahl, née Grosset (26 July 1872, in Boromlya, Poltava Region – 6 January 1972) was a Ukrainian-born German zoologist, arachnologist, and carcinologist.

[1] Maria Johanna Grosset was born on 26 July 1872 in Boromlya, Russian Empire (currently in Poltava Region, Ukraine).

[5] From 1892 to 1899 Dahl was employed as an assistant to Karl Brandt at Zoological institute in Kiel where she was working with the collections from the 1889-90 Plankton-Expedition.

[5] In the foreword to her analysis of the copepod genus Corycacinen, Dahl apologized for not having a PhD in zoology and for taking too long to complete the task.

[2] A review in Nature called Die Tierwelt Deutschlands "a reference book necessary to every library of zoology", noting that "each species is given an excellent and well-illustrated systematic description".