I6

I6 or I-6 may refer to:
 * JAPANESE SUBMARINE I-6, an Imperial Japanese Navy submarine launched in 1935 and sunk in 1944
 * Polikarpov I-6, a Soviet fighter prototype of the 1930s
 * Straight-six engine, six-cylinder internal combustion engine
 * Ravenloft (module), or "I6: Ravenloft," a 1983 adventure module for Dungeons & Dragons
 * Roewe i6, a Chinese saloon

I 6 is a Swedish regimental designation (6th Infantry Regiment) that has been used by the following units:
 * Västgöta Regiment (1816–1927)
 * North Scanian Infantry Regiment (1928–1963)