Which is the largest crater in the Solar System?
Before 2020, the largest known crater in the Solar System was the North Polar Basin on Mars. However, in 2020, scientists discovered what appears to be an even larger crater on Jupiter's moon Ganymede1. Although we can't yet be sure, it appears to be an impact crater with a diameter of 15,600 km (9,693 miles). This would make it by far the largest crater—the North Polar Basin is 10,600 km (6,550 mi) wide at it's widest point.
Scientists think this crater may have been formed by an impact from another object about 150 km (93 mi) in diameter.
Until it is confirmed as a crater (or other geological feature) it doesn't have an official name.
Jupiter's moon Ganymede, with what could be the largest crater in the Solar System.
Credit: Tsunehiko Kato, 4D2U Project, NAOJ
Footnotes
[1] Press release from Kobe University, Japan: https://www.kobe-u.ac.jp/research_at_kobe_en/NEWS/news/2020_08_05_01.html