No, Cornwall does not have the biggest coastline in the world.

While Cornwall has a significant coastline, it pales in comparison to other countries and regions with vast coastlines.

Here's why:

* World's Longest Coastline: Canada holds the title for the world's longest coastline, stretching over 240,000 kilometers (150,000 miles).

* Comparison to Cornwall: Cornwall's coastline is approximately 496 kilometers (308 miles) long.

Therefore, Cornwall's coastline is significantly smaller than Canada's and many other countries with extensive coastlines.