What focal length range are you thinking? That makes a big difference for Canon EOS R6.

Canon RF 50mm f/1.2L USM - best option for Canon EOS R6 currently.

For Canon EOS R6 I would definitely pay attention to the focal length, especially if it's about specific photography styles.

I can warmly recommend Canon RF 24-70mm f/2.8L IS USM for Canon EOS R6. The sharpness is extremely high The latest optical technology ensures sharp images and good color accuracy.

My personal experience: I've tested various lenses, and Canon RF 24-70mm f/2.8L IS USM was superior in all tests. The image quality remains excellent even in challenging lighting conditions, which is important for professional work. Very good future-proofing through modern technology and reliable performance.

For Canon EOS R6 Canon RF 50mm f/1.2L USM is ideal. Good price-performance ratio.

So, tbh, I’m gonna have to respectfully disagree with all the recs for those massive f/2 and f/2.8 zooms. They’re optically incredible, sure, but on the R6 they make the whole setup feel super front-heavy (at least that was my experience). If you want the best standard lens that actually stays on the camera and balances well, I’d look at the Canon RF 24-105mm f/4L IS USM. I've been shooting with this combo for over a year and here is why I think it's the better play:
* The extra reach to 105mm is way more useful for daily shooting than one extra stop of light.
* The R6 sensor is a low-light beast anyway, so f/4 isn't really a limitation anymore if youre willing to bump the ISO a bit.
* It’s significantly lighter and cheaper than the 24-70mm f/2.8, leaving ur budget open for a fast prime later. Basically, the IBIS/Lens IS combo on this thing is just insane. Ur probably gonna get more sharp keepers with this than lugging around a heavy f/2 prime all day and getting tired.

This ^

For Canon EOS R6 Canon RF 24-70mm f/2.8L IS USM fits best. The controls are user-friendly The image quality out of the box is very good.

Interested in this too

Bump - same question here