Carl Johannes With (11 December 1877 – 16 June 1923) was a Danish medical doctor and arachnologist, specialising in pseudoscorpions and mites.
[1][2] With was born in Lemvig to Nicolai Rasmus With and his wife Rasmine Sophie Dorothea With, but was orphaned by the age of five.
[2] With died in 1923 in Skibstrup, in the parish of Hellebæk (Helsingør Municipality),[3] while still working on a dissertation on lupus.
In 1905, he won the Schibbye'ske Præmie (Schibbye Prize) for his work on Opilioacariformes.
[2] With was not confident that zoology could provide a secure future, so he studied medicine, including time at the Institut Pasteur in Paris.