Marius Nicolae Crainic (February 3, 1973, Aiud) is a Romanian mathematician working in the Netherlands.

Born in Aiud, Romania, Crainic obtained a bachelor's degree at Babeș-Bolyai University (Cluj-Napoca) in 1995.

He then returned to Utrecht University as a Fellow of the Royal Netherlands Academy of Arts and Sciences (KNAW).

[6][7] In July 2020 he was an invited speaker to the 8th European congress of Mathematics,[8] which has been rescheduled to 2021 due to the COVID-19 pandemic.

[25] Among his most well-known results are a solution to the long-standing problem of describing the obstructions to the integrability of Lie algebroids[26] and a new geometric proof of Conn's linearization theorem,[27] both written in collaboration with Rui Loja Fernandes, as well as the development of the theory of representations up to homotopy.