The hub of the 33-branch OPL system, the Main branch the largest library in the system, with the greatest selection of material of all kinds and the most public access Internet stations in the city. Located downtown in the heart of the business and government communities, the Main branch is the place for reference services, including the Ottawa Room, which holds an extensive collection of local historical documents. This branch has a Friends of the Ottawa Public Library Association (FOPLA) used book store.

The Main branch received these improvements in 2014.

• Renovated children’s area including a new floor plan with improved sight lines
• Furniture upgrades
• Increased public space on the 3rd floor
• Consolidation of all bookable public internet computers for adults, on the 3rd floor
• RFID technology installation
• New point of service