Mare Nectaris is a lunar sea, or maria, one of the darker on the near side of the Moon. It is about 210 miles across and filled with dried lava.

Above it is Sinus Asperitatis, Latin for "Bay of Roughness". This "bay" joins Mare Nectaris to Mare Tranquillitatis.

Three craters line Mare Nectaris to the west.

Theophilus crater is named after Theophilus I of Alexandria (bef. 384 - 412), the 23rd Pope of Alexandria. He wrote a Paschal table that tracks the Moon's phases to aid in determining the date of Easter.

Cyrillus crater is named after Saint Cyril of Alexandria (c. 376 - 444), the 24th Pope of Alexandria. He also constructed a Paschal table to calculate the date of Easter.

Catharina crater is named for Saint Catherine of Alexandria (c. 287 - c. 305), a martyr and early adopter of Christianity in the Roman empire. However, there is little evidence to support her existence as a historical figure.

A few craters lie to the south of Mare Nectaris:

Beaumont crater is named for the French geologist Léonce Élie de Beaumont (1798-1874) who proposed a theory for the origin of mountain ranges. He proposed that all mountains parallel to each other were formed at the same time.

Fracastorius crater is named for the Italian scholar Girolamo Fracastoro (c. 1476 - 1553). He was an early adopter of the idea of "atoms" and was one of the first to study epidemiology. He worked extensively on the origins of rabies and syphilis.

Rosse crater is named after the English astronomer William Parson, 3rd Earl of Rosse (1800-1867). He built one of the world's largest telescopes, the "Leviathan of Parsonstown", a 72-inch telescope. Through it, he observed nebulae and galaxies, such as the Crab Nebula and Whirlpool Galaxy.

Finally, two craters lie to the northeast of Mare Nectaris:

Isidorus crater is named after Isidore of Seville (c. 560 - 636), the archbishop of Seville. He was a prominent figure in early Spanish Christianity, and wrote down his Etymologiae, an encyclopedia of knowledge at the time.

Capella crater is named for Martianus Capella (bef. 410 - 420), a Latin scholar who wrote De nuptiis Philologiae et Mercurii "On the Marriage of Philology and Mercury". In the eighth book of the series, he describes a modified geocentric model of the solar system, where all planets orbit the Earth, except for Mercury and Venus which orbit the Sun.