A family of iridium(I) hydroxides of the form [Ir(cod)(NHC)(OH)] (cod=1,5-cyclooctadiene, NHC=N-heterocyclic carbene) is reported. Single-crystal X-ray analyses and computational methods were used to explore the structural characteristics and steric properties of these new complexes. The model complex [Ir(cod)(IiPr)(OH)] (IiPr=1,3-(diisopropyl)imidazol-2-ylidene) undergoes reaction with a wide variety of substrates including boronic acids and silicon compounds. In addition, O-H, N-H and C-H bond activation was achieved with alcohols, carboxylic acids, amines and various sp-, sp- and sp -hybridised carbon centres, giving access to a wide range of new Ir complexes. These studies have allowed us to explore the exciting reactivity of this motif, revealing a versatile and useful synthon capable of activating important chemical bonds under mild (typically room temperature) conditions. No additives were required and, in the case of X-H bond activation, water was the only waste product, rendering this an atom efficient procedure for bond activation. This system has great potential for the construction of new catalytic cycles for organic synthesis and small-molecule activation.