Eir Aoi (Japanese: 藍井エイル, Hepburn: Aoi Eiru, born November 30, 1988) is a Japanese singer from Sapporo, Hokkaido, signed to Sacra Music. After being discovered through the Japanese video sharing website Niconico, Aoi made her major debut in 2011 with the release of her first single "Memoria", whose title track was used as the first ending theme to the 2011 anime television series Fate/Zero.

Aoi's music has been featured in various anime television series such as Sword Art Online, Kill la Kill, and The Heroic Legend of Arslan, as well as other television programs such as Rank Okoku. She has performed at various anime conventions in Asia, Europe, North and South America. She has cited her interest in anime, as well as artists such as Evanescence, Slipknot, and Do As Infinity, as influences in her career. In October 2016, following prolonged bouts of poor health, she announced an indefinite hiatus from musical activities following a two-day concert at the Nippon Budokan in November 2016. In February 2018, it was announced that she would resume her activities later that year.