Vsevolod Mavrikievich Klechkovsky, also transliterated as Klechkovskii and Klechkowski (November 28 1900 in Moscow - May 2 1972 in Moscow) was a Soviet-era agricultural chemist known for his work with radioisotopes. His use of isotopic labeling in the advance of soil chemistry led to his being considered a founder of agricultural radiology.

Following the 1957 Kyshtym disaster, Klechkovsky led the research projects studying the long-term effects of radioactive contamination at the site.

Klechkovsky also studied theoretical chemistry, and proposed a theoretical justification of the empirical Madelung rule for the ordering of atomic orbital energies. This rule is therefore sometimes called Klechkovsky's rule.