For Canon EOS RP I would also consider the aperture. Do you need fast lenses for low light?

Am very satisfied with Canon RF 85mm f/1.2L USM for Canon EOS RP. The design is modern and compact The build quality feels premium and should last for years.

For Canon EOS RP, Sigma 85mm f/1.4 DG DN Art is an excellent choice. The price-performance ratio is great The image quality out of the box is very good.

Additionally, you should note: The latest generation offers significantly better image quality than previous models. Especially ideal for demanding photography and video work. Compatibility with Canon EOS RP is very good, and the autofocus performance is also convincing.

Have you thought about the brand? For Canon EOS RP different brands have advantages.

Have good experience with Sigma 85mm f/1.4 DG DN Art for Canon EOS RP. The image quality is excellent The performance eliminates chromatic aberration effectively.

Came here to say the same thing lol. Great minds think alike I guess.

Canon RF 50mm f/1.2L USM is my recommendation for Canon EOS RP. Works great!

So I totally agree about the balance thing - slapping a massive piece of glass on the RP basically turns it into a grip for the lens rather than a camera. I have been shooting with this setup for a while and honestly, the Canon RF 85mm f/2 Macro IS STM is the real sweet spot that hasn't been mentioned yet. It is way lighter than those f/1.2 monsters or the heavy Art lenses and it balances perfectly on the small RP body. The main reason I love it tho is the Image Stabilization. Since the RP doesnt have IBIS, having that stabilization built into the lens is a total lifesaver for handheld work. A few things from my experience:

• The bokeh is surprisingly smooth for an f/2 lens
• Having the macro capability is a huge bonus for close-up detail shots like eyes or jewelry
• It stays sharp even wide open Tbh if you arent shooting in a pitch-black room, f/2 gives you plenty of background blur. Your wrists will definitely thank you after a long shoot too. It is just a much more practical daily driver for the RP than the heavy L series glass.

Ok so we've seen a lot of solid high-end suggestions here, ranging from the ultra-fast 1.2 primes to some versatile third-party zooms. But honestly, one thing I HAVE to mention—especially since you're using the EOS RP—is the issue of ergonomics and balance. The RP is a really small, lightweight body, and if you slap a massive 1.2L or a heavy Art lens on it without an extension grip, it gets super front-heavy. I've seen so many people buy these 'dream' setups only to find them incredibly tiring to hold for an actual shoot. Also, just a quick heads-up to be careful with compatibility; some of those third-party lenses mentioned might be for different systems or require the EF-RF adapter, which adds even more length and bulk. Basically, make sure you're not just looking at the image quality but how the whole rig actually feels in your hand. I think it's a mistake to overlook the weight distribution, tbh. You don't want a setup that feels totally awkward to use after twenty minutes!

I really agree with what Daniel said about the weight distribution. When I first got my RP, I was terrified of it being too front-heavy and maybe slipping out of my hands or just being awkward to carry around all day. Honestly, if you want to keep things simple and safe, you cant go wrong with the Canon RF 50mm f/1.8 STM. It is super light, costs way less than the L-series glass (usually under $200), and since it is a native Canon lens, you dont have to worry about any weird autofocus glitches or using adapters. I have been using it for about six months now and the results are honestly great for the price. It might not be as fancy as an f/1.2, but for a beginner like me, the reliability and the size made it a no-brainer for portraits. Just makes the whole setup feel way more secure in my hands.