MamoUsa

UsagixMamoru, sometimes known as Moonshipping is a het ship between Usagi Tsukino (aka Sailor Moon and Princess Serenity) and Mamoru Chiba (aka Tuxedo Mask, Prince Endymion, and Moonlight Knight) in the Sailor Moon series.

Canon
At some point in the distant past Princess Serenity and Prince Endymion fell in love. But this caused a war between the Earth and the Moon causing the destruction of the Moon Kingdom.

They are reborn as Usagi Tsukino and Mamoru Chiba. They don't get along at first but soon fall in love again.

Fanon
It is among the most popular shippings.