UIN

UIN may refer to:

Common

 * User Identification Number, used by many computer security systems and ICQ, see ICQ, Unique identifier and User (computing)
 * Universal Identification Number
 * used for people, see National identification number and Unique Identification Authority of India, see also Permanent account number (PAN)
 * used for inventory, see also UID
 * University Identification Number, used by many universities for students, faculty and alumni
 * Unit Identification Number, used by the military, see Military unit
 * Unit Identification Number, used by the Department of Education, see Integrated Postsecondary Education Data System
 * Unique Identification Number, similar to Universal Identification Number used for people and inventory, see above, and often replaced by Universally unique identifier (UUID)

Other uses

 * User Intelligent Network, a type of network artificial intelligence, see, for example Personal communications network
 * Airport code for Quincy Regional Airport in Illinois, United States