Thiocyanates are salts containing the thiocyanate anion [SCN]⁻ (also known as rhodanide or rhodanate). [SCN]⁻ is the conjugate base of thiocyanic acid. Common salts include the colourless salts potassium thiocyanate and sodium thiocyanate. Mercury(II) thiocyanate was formerly used in pyrotechnics.

Thiocyanate is analogous to the cyanate ion, [OCN]⁻, wherein oxygen is replaced by sulfur. [SCN]⁻ is one of the pseudohalides, due to the similarity of its reactions to that of halide ions. Thiocyanate used to be known as rhodanide (from a Greek word for rose) because of the red colour of its complexes with iron.

Thiocyanate is produced by the reaction of elemental sulfur or thiosulfate with cyanide:

The second reaction is catalyzed by thiosulfate sulfurtransferase, a hepatic mitochondrial enzyme, and by other sulfur transferases, which together are responsible for around 80% of cyanide metabolism in the body.

Oxidation of thiocyanate inevitably produces bisulfate. The other product depends on pH: in acid, it is hydrogen cyanide, presumably via HOSCN and with a sulfur dicyanide side-product; but in base and neutral solutions, it is cyanate.

Thiocyanate occurs widely in nature, albeit often in low concentrations. It is a component of some sulfur cycles.

Thiocyanate hydrolases catalyze the conversion of thiocyanate to carbonyl sulfide and to cyanate:

Thiocyanate is known to be an important part in the biosynthesis of hypothiocyanite by a lactoperoxidase. Thus the complete absence of thiocyanate or reduced thiocyanate in the human body, (e.g., cystic fibrosis) is damaging to the human host defense system.