CTO
- CTO Hospital (Turin)
- Cancelled-to-order
- Cape Town Opera
- Caribbean Tourism Organization
- Central Treaty Organization
- Certified Television Operator
- Chief Technology Officer of the United States
- Chief technology officer
- Chronic total occlusion
- City ticket office
- Color correction
- Commonwealth Telecommunications Organisation
- Community treatment order
- Configure-to-order
- Cyprus Tourism Organisation
- Tall Oil