SMX may refer to:
As an abbreviation:
- SMX (operating system), a Unix-like simulator on SPARC, the "SunOS/Solaris MINIX"
- Standard Musical Expression, a representation of simple music in ASCII that was used in some DOS software such as QBasic
- SMX Convention Center (company), an events venue management company in the Philippines
- SMX Convention Center Manila, Pasay, Philippines
- Sulfamethoxazole, an antibiotic
- Honda S-MX, a minivan
- Spatial multiplexing, MIMO wireless transmission technique
- Singapore Mercantile Exchange
- SmX RNA and SmY RNA, ribonucleic acids in nematode worms
- S.M.X., director of Revelation at the 1999 New York Underground Film Festival
- StepManiaX, a rhythm game by Step Revolution
As a code:
- Santa Maria Public Airport, in California, US, IATA code
- C.A.I. First, regional Italian airline, ICAO airline code
- SMTC Corporation, Canada, TSX/Toronto ticker code
- Sanmenxia city in Henan, China, governmental code SMX
- Sendmail X, now MeTA1, mail server coded smX
- Special Mobile Machine—Exempt, prefix SMX, on vehicle registration plates of Colorado