Iridium(III) chloride is the inorganic compound with the formula IrCl<sub>3</sub>. The anhydrous compound is relatively rare, but the related hydrate is much more commonly encountered. The anhydrous salt has two polymorphs, α and β, which are brown and red colored respectively. More commonly encountered is the hygroscopic dark green trihydrate IrCl<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub> which is a common starting point for iridium chemistry.
Hydrated iridium trichloride is obtained by heating hydrated iridium(III) oxide with hydrochloric acid. This is the monoclinic α polymorph. A rhombohedral β polymorph also exists. Both polymorphs have effectively the same anion lattice but differ in the octahedral interstices the iridium ions occupy. The α polymorph converts to the β polymorph when heated to around 650 °C. With the presence of the chloride anion, it forms hexachloroiridate(III), and produces hexachloroiridate(IV) in aqua regia. The trihydrate react with ammonia to form ammine complexes, such as pentaamminechloroiridium(III) chloride, formulated [IrCl(NH<sub>3</sub>)<sub>5</sub>]Cl<sub>2</sub>. It also reacts with concentrated ammonium hydroxide at 150 °C to form the fully ammoniated complex, [Ir(NH<sub>3</sub>)<sub>6</sub>]Cl<sub>3</sub>. The hydrate can also form complexes upon reaction with bipyridine, acetonitrile, and pyridine.
Alkene complexes such as cyclooctadiene iridium chloride dimer and chlorobis(cyclooctene)iridium dimer
:2 IrCl<sub>3</sub> + 3 H<sub>2</sub> → 2 Ir + 6 HCl