By client
- O4BO
- Oakland County, Michigan
- OCBC Bank
- Oceanet Technology
- OCH Regional Medical Center
- Odyssey Logistics & Technology Corporation
- Odyssey Transportation & Logistics Corporation
- Office Depot
- Office des Postes et Télécommunications de Polynésie (OPT)
- OfficeMax
- OGSI (Online Game Services Inc.)
- OhioHealth
- OKI Printing Solutions
- Oklahoma Department of Human Services
- OLM Systems
- OMERS
- Omnicom Group Inc.
- Omron Europe
- OMV Gas & Power GmbH
- Oncor Electric
- Oncor
- One of the largest banks in Southeast Asia
- OneTree Solutions
- Online Backup Company
- Online content provider
- Open Futures
- OpenLogix Corp.
- Open Universities Australia
- Options IT
- Orange Business Services
- ORGA
- Oriflame Cosmetics
- Original Equipment Supplier Association (OESA)
- Orvis
- Ospedale San Raffaele
- OTP Bank
- Oxfordshire County Council in the UK
- Oxxio