I3, I-3 or i3 may refer to: Science and technology Core i3, a microprocessor line from Intel i3 (window manager), a tiling window manager Triiodide (I3−), an anion composed of 3 iodide atoms Intermud-3, an InterMUD network method between MUDs Axiom I3, a large cardinal axiom in rank-into-rank set theory Transport Interstate 3, a proposed Interstate Highway in the U.S. states of Georgia and Tennessee BMW i3, an electric car by BMW Inline-triple engine, an internal combustion engine with three cylinders in a straight line LB&SCR I3 class, a British LB&SCR locomotive Military , a Type J1 submarine of the Imperial Japanese Navy i3 fighter, a conceptual Japanese jet fighter proposed in 2010 Mikoyan-Gurevich I-3, a heavy interceptor prototype fighter of the 1950s Polikarpov I-3, a 1928 Soviet biplane fighter See also 3i, a company headquartered in London, United Kingdom