Alexander Onufrievich Kovalevsky (Russian: Алекса́ндр Ону́фриевич Ковале́вский; 7 November 1840 – 1901) was a Russian embryologist, who studied medicine at the University of Heidelberg and became professor at the University of St Petersburg.

[1][2][3][4] He was the brother of the paleontologist Vladimir Kovalevsky, and the brother-in-law of the mathematician Sofya Kovalevskaya.

[1][2][3][4] Kovalevsky discovered that tunicates are not molluscs, but that their larval stage has a notochord and pharyngeal slits, like vertebrates.

19th-century zoology thus converted embryology into an evolutionary science, connecting phylogeny with homologies between the germ layers of embryos, foreshadowing evolutionary developmental biology.

[5] He was elected on the 1st of May 1884 a Foreign Member of the Linnean Society of London.