OPSI may stand for:

• Overwhelming post-splenectomy infection, rapidly fatal septicaemia in a patient who has undergone splenectomy (removal of the spleen).
• Office of Public Sector Information, a UK government body incorporating Her Majesty's Stationery Office.
• Open PC Server Integration An open source systems management system with the emphasis on automating software deployment on Windows clients, based on a Linux server.

• Raja Beni Mellal
• Raja Bersiong
• Rajabhai tower
• Raja Bhaiya
• Raja Bhaiyya
• Rajabhat Institute
• Rajabhatkhawa
• Rajabhat universities
• Rajabhat Universities
• Rajabhat University
• Rajabhat University system
• Raja Bhoj Airport
• Raja binoculata
• Rajabi Tower
• Rajab Mwinyi
• Raja Brooke
• Rajab ul Murajjab
• Rajab ul Murrajjab
• Raja Chinna Roja
• Raja Chulan
• Raja Chulan Monorail station
• Raja clavata
• Raja Club Athletic
• Raja College of Engineering and Technology
• Rajaconda