It is the only one of the lunar maria to be called an "Oceanus" (ocean), due to its size: Oceanus Procellarum is the largest of the maria ("seas"), stretching more than 2,500 km (1,600 mi) across its north–south axis and covering roughly 4,000,000 km2 (1,500,000 sq mi), accounting for 10.5% of the total lunar surface area.

[2] Like all lunar maria, Oceanus Procellarum was formed by ancient volcanic eruptions resulting in basaltic floods that covered the region in a thick, nearly flat layer of solidified magma.

On its north-west edge lies the 32 km wide Aristarchus ray crater, the brightest feature on the Near side of the Moon.

One piece of evidence in support of this hypothesis is concentration of incompatible elements (KREEP) and low calcium pyroxene around Oceanus Procellarum.

[7] The GRAIL mission, which mapped the gravity gradients of the Moon, found square formations resembling rift valleys surrounding the region beneath the lava plains, suggesting the basin was formed by heating and cooling of the lunar surface by internal processes rather than by an impact, which would have left a round crater.

The Chinese probe Chang'e 5 landed at Statio Tianchuan on Mons Rümker in Oceanus Procellarum in December 2020 and collected 1.73 kg (3.8 lb) of lunar rock samples.

During the November 1969 Apollo 12 mission, astronauts (Charles) Pete Conrad and Alan Bean landed the Lunar Module (LM) Intrepid nearly 165 meters from Surveyor 3 in Oceanus Procellarum.