Brissus unicolor is a species of sea urchins of the family Brissidae.

[1] The urchin buries itself in the coarse sand at depths of 6 to 250 meters (which is why it is rarely observed alive).

In the Mediterranean Sea they can be sometimes found living buried in the sediment near the tapeweed, Posidonia oceanica.

After the urchin dies, its shell (also called a "test") has a distinctive pattern that consists of many grey spots.

This species lives in the Mediterranean Sea and some parts of the Atlantic Ocean.