- DIIS stands for Danish Institute for International Studies (Denmark)
- DIIS stands for Direct Inversion in the Iterative Subspace (Pulay mixing)
- DIIS stands for Draft Integrated Impact Statement (community study; Australia)
- DIIS stands for Diatomics-In-Ionic-Systems
- DIIS stands for Directorate for Intelligence and Information Security
- DIIS stands for DECCO Integrated Information System
DIIS