DII

DII may refer to:
 * Days in inventory, an accounting term
 * Dii, the Thracian tribe
 * Dii language
 * DiI, a hydrophobic cyanine dye used in cell biology
 * Dietary Inflammatory Index
 * Delegation of the Ismaili Imamat, the Delegation of the Ismaili Imamat
 * Diablo II, a sequel to the computer game Diablo
 * Division II, a competition level in the National Collegiate Athletic Association (NCAA)
 * Defence Information Infrastructure, the UK's secure military communications network
 * Dynamic Invocation Interface, part of the CORBA standard
 * 502, DII in Roman numerals