What is the best fisheye lens?

The best fisheye lens often depends on your specific needs and camera system. For full-frame cameras, the Nikon 8-15mm f/3.5-4.5E ED is highly regarded for its versatility and image quality, offering both circular and full-frame fisheye perspectives. For those using crop sensors, the Rokinon 8mm f/3.5 is a budget-friendly option that delivers Excellent results. Ultimately, the best choice will vary based on factors like budget, desired focal length, and intended use.