Mine is biggest…
The biggest Canon lens ever made is the Canon Super Telephoto 1200mm f/5.6L EF USM Autofocus Lens. Yep, 1200 mm, that’s very long.
It has a maximum diameter of 22.8 cm, a maximum length of 83.6 cm and it weighs 16.5kg. So you might buy a sturdy tripod with that.
Less that 20 of them are made and Sports Illustrated owns two of them, as well as James Jannard (the founder of the eyewear and apparel company Oakley, Inc.) and National Geographic might have one or two as well.
Canon built them by order from 1993 to 2005, each lens was hand-crafted at the rate of about 2-per-year and a delivery time of about 18 months.
The price of the thingie? 52740 euros. Quite cheap for a toy like that but sometimes you can buy them second-hand too.