Dimethyl selenide is the organoselenium compound with the formula (CH3)2Se.

This colorless, malodorous liquid is the simplest selenoether.

It occurs in trace amounts in anaerobic environments[1] and in the atmosphere due to biomethylation of selenium.

[2][3] Dimethyl selenide is prepared by treating Se2− sources with electrophilic methylating agents such as methyl iodide: The carbon–selenium bond length is 1.943 Å and the C–Se–C bond angle is 96.2°, as determined by microwave spectroscopy.

[4][5] Similar dimensions of 1.98 Å and 98° are found by gas electron diffraction.