TMO stands for:
- Table Mountain Observatory, California
- Tortugas Mountain Observatory, New Mexico, USA
- Thermo Electron NYSE code
- Tenant management organisation, a term especially used in the United Kingdom
- Transition-Metal Oxide (see also Surface properties of transition metal oxides)
- Television Match Official, an official in both rugby union and rugby league who assists the referee in determining whether points have been scored. (The term "video referee" is also used, especially in league.)
- Traffic Management Order, an order made by a United Kingdom local authority under the Road Traffic Regulation Act 1984 which details the nature and extent of traffic and parking controls within the council’s area. It is a contravention of these controls that may give rise to the issuing of a Penalty Charge Notice. The same orders are known as Traffic Regulation Orders (TROs) outside London.