S9 may refer to:
==Transportation== SIAI S.9, a 1918 Italian flying boat Aircraft registration prefix of São Tomé and Príncipe USS S-9 (SS-114), a 1920 S-class submarine of the United States Navy County Route S9 (California) Rans S-9 Chaos, a light aerobatic aircraft East African Safari Air's IATA code
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).