IEO

IEO may refer to:


 * Independent Evaluation Office, of the World Bank
 * International English Olympiad, a competition conducted by the Science Olympiad Foundation
 * Istituto Europeo di Oncologia, the European Institute of Oncology
 * Interior-Earth object or Atira asteroid
 * Institut d'Estudis Occitans (Institute of Western Studies), a cultural organization
 * Initial exchange offering