Momoyo Koyama (Japanese: 小山 百代, Hepburn: Koyama Momoyo, born November 30, 1995) is a Japanese actress, voice actress and singer from Sapporo, Hokkaido, who is affiliated with Stardust Promotion. She is known for playing Sailor Mercury in two stage play adaptations of Sailor Moon in 2014 and 2015, and for playing Karen Aijō, the protagonist of the multimedia franchise Revue Starlight. She is also a member of the musical group SoundOrion