- Oath
- Obiter Dictum
- Object
- Objection
- Objective Theory of Contract
- Obligation
- Obligee
- Obligor
- Obliteration
- Obscene
- Obscenity
- Obstruction of Justice
- Occupancy
- Occupational Disease
- Occupational Safety and Health Act of 1970
- O'Connor, Sandra Day
- O'Conor, Charles
- Of Counsel (Definition)
- Of Course
- Of Record
- Offense
- Offer
- Office Audit
- Office of Management and Budget
- Office of National Drug Control Policy
- Office of Thrift Supervision
- Officer
- Officers of the Court
- Official Gazette
- Offset
