The Canon FD 300mm f/4 is a manual-focus telephoto prime for Canon's FD mount, the breech-lock and later New FD bayonet system used on Canon SLRs between 1971 and 1987. Designed for sports, wildlife and long-reach portraiture, it sits a stop slower than the professional FD 300mm f/2.8 L but is far more compact and affordable, which is largely what determines its value on the used market today.

At UK auction the FD 300mm f/4 is firmly a budget telephoto: hammer prices in the SALES HISTORY run from £40 to £60, with a median around £56, reflecting wholesale saleroom levels rather than dealer retail. Clean, fungus-free copies sell for the upper end of that band, while examples with cosmetic wear or optical faults are worth closer to the £40 floor. As of 2026 there is no clear premium for any one variant in the recorded data, and demand is driven mainly by adapter users on mirrorless bodies asking what a usable long FD prime is worth.