VCO may refer to:
- Voltage-controlled oscillator, an electronic device.
- Voice Carry Over (Telecommunications Relay Service).
- Viceroy's Commissioned Officer
- Voyage Century Online, a free nautical MMORPG developed by Snail Games and published by IGG, distributed in Europe as Bounty Bay Online.
- VMware vCenter Orchestrator (vCO).
- Akatsuki space probe, also known as Venus Climate Orbiter.
- Vrais chrétiens orthodoxes : l'Église orthodoxe de la pure Tradition chrétienne, cf.: http://orthodoxievco.net/