In organic chemistry, thiepine (or thiepin) is an unsaturated seven-membered heterocyclic compound, with six carbon atoms and one sulfur atom. The parent compound, C<sub>6</sub>H<sub>6</sub>S is unstable and is predicted to be antiaromatic. Bulky derivatives have been isolated and shown by X-ray crystallography to have nonplanar C<sub>6</sub>S ring.
Computational studies suggest that thiepine would eliminate a sulfur atom to form benzene. The intermediate is this process is the bicycle thianorcaradiene. In the complex with (÷<sup>4</sup>-C<sub>6</sub>H<sub>6</sub>S)Fe(CO)<sub>3</sub>, the ring is stable.
Benzothiepines have one fused benzene group and dibenzothiepines such as dosulepin and zotepine have two fused benzene groups. Damotepine is another thiepin derivative.