What is the name of the gap in Saturn's rings caused by Mimas?

The gap in Saturn’s rings associated with Mimas is the Cassini Division. It is the broad, relatively dark separation between Saturn’s bright B Ring and A Ring.

Giovanni Domenico Cassini identified the division in 1675 while observing Saturn through a refracting telescope. Although it looks nearly empty from Earth, the region is not a perfect vacuum: Voyager observations showed that it contains diffuse ring material and numerous narrow ringlets.

Mimas helps maintain the division through orbital resonance. Near the division’s inner edge, ring particles orbit twice for every one orbit completed by Mimas. The moon’s repeated gravitational tugs destabilize particles in those resonant orbits, clearing material and producing a sharp boundary in ring density.

The name can cause a terminology mix-up. Astronomers often call broad separations between major rings “divisions,” while narrower openings within a ring are called “gaps.” The Encke Gap and Keeler Gap are narrower features in Saturn’s A Ring and are not the answer to this question. The Cassini Division is named for the astronomer, not directly for the Cassini spacecraft.