Casimir Albrecht Willem Jeekel (24 January 1922 – 13 March 2010) was a Dutch myriapodologist and entomologist known for his major contributions to the taxonomy of millipedes.

His 1971 monograph Nomenclator Generum et Familiarum Diplopodorum is credited as launching the "modern era" of millipede taxonomy, and has been considered the "most important single work ever published on the Diplopoda".

[2] He studied at the University of Amsterdam and his doctoral thesis, published in 1968, concerned the classification and geographic distribution of the Paradoxosomatidae, a large family of millipedes.

In 1969 he assumed the position of director of the Zoological Museum, a move which "greatly improved his standard of living, but at the expense of his research and health".

[8] Jeekel also made a modest contribution to mycology, the study of fungi, when in 1959 he described a new species of fungus in the genus Laboulbenia that parasitizes carabid beetles.