Methaneselenol is the organoselenium compound with the formula CH3SeH.

A colorless, poisonous gas, it is notorious for its foul, putrid odor.

It is prepared by reaction of methyl lithium or a methyl Grignard reagent with selenium followed by protonation of the product.

[1][2] According to IR spectroscopy, νSe-H = 2342 cm−1.

For the other homologues, νE-H = 1995 (E = Te), 2606 (E = S), and 3710 cm−1 (E = O) for methanetellurol, methanethiol, and methanol.