Yes, you can install an NVIDIA RTX 4090 in the Fractal Design Focus G case. Here are some important details to keep in mind:

- The case supports graphics cards up to 380mm in length, and the NVIDIA RTX 4090 is typically around 304mm in length, which is within that limit.
- There is enough space for the graphics card without compromising the hard drive slots.

However, it is advisable to check the exact dimensions of your specific RTX 4090 card to make sure it will fit without any problems.