OSIS or similar terms may refer to:
OSIS Open Source Information System Open Scripture Information Standard A student council in Indonesia (Organisasi Siswa Intra Sekolah)
-osis The suffix -osis is used for forming a number of medical terms. The suffix itself signifies only a general functional disorder, but the constructed words are more specific. It is often used to denote a biological process (i.e. Apoptosis, Phagocytosis, Necrosis...)
Osis Osis (feminine: Ose) is a Latvian language surname meaning "ash" (tree; Fraxinus excelsior). Guntis Osis (born 1962), Soviet Latvian bobsledder Karlis Osis (1917–1997), paranormal researcher
See also OSI (disambiguation) for OSIs, the plural of OSI