Iridium (Ir) is a metallic chemical element with atomic number 77. The most abundant iridium isotope is ¹⁹³Ir, with 77 protons and 116 neutrons.

Iridium is the most corrsion-resistant of all metals. One of its industrial applications, when alloyed with other metals, is in the spark plugs used in ignition systems of car and airplane engines.