• The Institut d'Informatique d'Entreprise, one of the French public Grandes écoles of engineering, specializing in computer science
• The Institute for International Economics, a think tank focused on international economics, based in Washington, D.C.
• The Institute of Industrial Engineers, the world's largest professional society for industrial engineering professionals, based in the United States
• The Institute of International Education, a world leader in the international exchange of people and ideas
• The Institution of Incorporated Engineers, the UK's largest multidisciplinary engineering association
• The Instituto de Investigaciones Estéticas, an art history research institute at Mexico's National Autonomous University (UNAM)
• Indian Institute of Entrepreneurship
• The Apple IIe.
• The Intrepid Interstellar Explorer, a proposed mission to send a probe to the heliopause.

iie can stand for:

• "No," in Japanese