I1

I1, i1, or I-1 may refer to:


 * Haplogroup I-M253, a human Y-chromosome haplogroup occurring at greatest frequency in Scandinavia
 * JSUB I-1, a 1926 Imperial Japanese Navy submarine
 * Motorola i1, a smartphone by Motorola
 * LB&SCR I1 class, a 1906 British class of 4-4-2 steam tank locomotives
 * Polikarpov I-1, a 1923 Soviet monoplane fighter
 * I1, a rank-into-rank axiom in mathematical set theory