Disulfur dinitride is the chemical compound with the formula S2N2.

Passing gaseous S4N4 over silver metal wool at 250–300 °C at low pressure (1 mmHg) yields cyclic S2N2.

The silver reacts with the sulfur produced by the thermal decomposition of the S4N4 to form Ag2S, and the resulting Ag2S catalyzes the conversion of the remaining S4N4 into the four-membered ring S2N2,[1] An alternative uses the less explosive S4N3Cl.

[2][clarification needed] S2N2 decomposes explosively above 30°C, and is shock sensitive.

Two π electrons from the sulfur atoms are coupled across the ring making the molecule overall a singlet diradical.