Yes and no. I have an S8+ and the Gear VR I got with my Note 7. It fits, but it's honestly too long to fit well. I can see content though. If you've got a regular S8 I'm pretty sure it'll fit fine though.
I just tried it with an S8+ and the VR from last year that's dark colored. Worked just fine. It's a tight fit, and probably sticks up 1/16th of an inch higher on the side that clicks in, than the side with the part that plugs in the phone, but I didn't have any issues. Watched an entire video, and seemed perfectly fine. I might be just imagining, it the pixels seem smaller than the S7 Edge. Less screen door effect