Carbonyl selenide is a chemical compound with the chemical formula O=C=Se. It is a linear molecule that is primarily of interest for research purposes.

Carbonyl selenide is a colorless gas with an unpleasant odor. Although the compound is quite stable, its solutions gradually revert to elemental selenium and carbon monoxide.

Carbonyl selenide can be produced by treating selenium with carbon monoxide in the presence of amines.

It is used in organoselenium chemistry as a means of incorporating selenium into organic compounds, e.g. for the preparation of selenocarbamates (O-selenocarbamates R−O−C(=Se)−NR'R" and Se-selenocarbamates, R−Se−C(=O)−NR'R", where R is organyl and R' and R" are any group, typically H or organyl).

Carbonyl selenide is believed to catalyze certain (oxidative and non-oxidative) carbonylation reactions.