Methylphosphine is the simplest organophosphine compound with the formula CH<sub>3</sub>PH<sub>2</sub>, often written MePH<sub>2</sub>. It is a malodorous gas that condenses to a colorless liquid. It can be produced by methylation of phosphanide salts:
The compound exhibits the properties characteristic of a primary phosphine, i.e., a compound of the type RPH<sub>2</sub>. It can be oxidized to methylphosphonous acid:
It protonates to give a phosphonium ion:
With strong bases, it can be deprotonated to give methylphosphanide derivatives: