The Canon EF 100-400mm f/4.5-5.6L is a telephoto zoom lens for the Canon EF autofocus mount, covering a 4x range from 100mm to 400mm with a variable maximum aperture of f/4.5 at the wide end and f/5.6 at the long end. As part of Canon's L-series professional line, it was designed for wildlife, sports and aviation photographers needing a versatile long-reach zoom on EF-mount SLR and DSLR bodies.

Auction data for this model is thin: a single UK saleroom hammer of £525 was recorded in April 2023, which sets the only datapoint we currently have for what a clean copy sells for at wholesale level. As of today in 2026, that figure should be treated as indicative rather than a firm market price, and condition, optical cleanliness and whether the lens is the original IS version or the later Mark II will materially affect value at auction. Buyers researching what a 100-400L is worth should weigh this hammer result against current dealer asking prices, which sit above auction levels once commission and warranty are factored in.