Deep-red- and near-infrared-phosphorescent tris-cyclometalated iridium(III) complexes bearing largely π-extended cyclometalated (C^N) ligands were newly synthesized, and their photo- and electroluminescence properties were investigated. When 2-(benzo[b]furan-2-yl)quinoline and 2-(benzo[b]thiophen-2-yl)quinoline were employed as C^N ligands, deep-red photoluminescence was obtained (Ir-1a and Ir-1b; λ PL in CH 2 Cl 2 , 647 and 652nm, respectively). In the case of the isoquinoline analogues of Ir-1a and Ir-1b, emission maxima were further red-shifted, ranging from deep-red to near-infrared regions (Ir-2a and Ir-2b; λ PL in CH 2 Cl 2 , 696 and 690nm, respectively). Especially, Ir-2b showed an excellent photoluminescence quantum yield (Φ PL =0.15), and a polymer light-emitting diode doped with Ir-2b exhibited deep-red–near-infrared electroluminescence with a high external quantum efficiency (λ EL =694nm, η ext max =1.41%).