Tri-nitrogen chloride (or TNC) is a chemical compound composed of chlorine ions and three nitrogen molecules.

Tri-nitrogen chloride was one of the substances used in plasma grenades. It was also used as a cleaning solution. In 2366, Thrax confronted Timor Landi with evidence that Timor and his Bajoran friends may have been handling plasma grenades, as suggested by epidermal scans revealing traces of tri-nitrogen chloride on their hands and clothes. Timor denied this, stating that the substance came from the cleaning solution he and his comrades had been using at Quark's. Thrax then countered that Timor may have used the opportunity of working at Quark's to obtain the compound for use in plasma grenades. (DS9: "Things Past")