OAP may refer to:

• OAP Tower, or Osaka Amenity Park Tower, a plaza and office development in Japan
• Old-age pensioner, a person who has retired, and now collects a pension, commonly referred to as an OAP in the United Kingdom
• One Australia policy, a proposal in the 1980s to limit Asian immigration to Australia
• Open access (publishing), a type of academic publication accessible by all, without subscription
• Offset Alpine Printing
• Off-axis parabolic reflector, a type of curved mirror used in optics and radio
• the Office of Atoms for Peace of Thailand