Can I use adapted lenses on the canon eos r?

Yes, and the Canon EOS R has a long list of lenses you can pair with it. Its catalogue page includes native Canon RF lenses plus third-party options from makers like 7Artisans, Laowa, TTArtisan, Samyang, Voigtländer and Zeiss. The page doesn't say which of those need an adapter, so check each lens's own page before you buy.

If you want a sensible start, I'd look at the Canon RF 50mm f/1.8 STM, the Canon RF 35mm f/1.8 Macro IS STM, or the Canon RF 24-70mm f/2.8L IS USM for a zoom. For the mount itself, see the Canon RF mount page.

Written by Claude from this site's pages.