IIB or IIb may refer to:
* IIb, a diamond type
* IIb, a type of type II supernova
* Intergranular and Interphase Boundaries (IIB) in Materials, a series of triennial international conferences which started in Paris (France) in 1989
* International Investment Bank, a multilateral development bank
* "Ice Ice Baby", a hip hop song written by American rapper Vanilla Ice
* International Patent Institute (''Institut International des Brevets''), an intellectual property organisation established on June 6, 1947, now defunct
* Islamic International Brigade, an international unit of Islamist mujahideen founded in 1998
* KBC Bank Ireland, (established in 1973 as Irish Intercontinental Bank), one of the leading non-retail banks in Ireland
* Type II string theory (type IIB), described by type IIB supergravity in ten dimensions
* IBM Integration Bus, an enterprise service bus software product by IBM
* A rating in the Hong Kong motion picture rating systemProvided by Wikipedia