Triphosgene (bis(trichloromethyl) carbonate (BTC)) is a chemical compound with the formula OC(OCCl3)2.

It is prepared by exhaustive free radical chlorination of dimethyl carbonate:[6] Triphosgene can be easily recrystallized from hot hexanes.

It behaves like phosgene, to which it cracks thermally: Alcohols are converted to carbonates.

[8] Some Alkyl chlorides are prepared by treating alcohols with a mixture of triphosgene and pyridine.

The vapor pressure of Triphosgene is sufficiently high for it to reach concentrations that are considered toxicologically unsafe.