Birthday (ClariS album)

Birthday is the debut studio album of the Japanese pop music duo ClariS, released on April 11, 2012 by SME Records. The album contains 12 music tracks, four of which were previously released on four of ClariS' singles. Three different editions of the album were released: a regular CD version, a two-CD limited edition and a CD+DVD limited edition. Birthday peaked at No. 2 on the Japanese Oricon weekly albums chart and was awarded a Gold Disc by the Recording Industry Association of Japan in May 2012.

Five of the songs were used as theme songs for various media: "Irony" was used as the opening theme to the 2010 anime television series Oreimo; "Koi Jishaku" was the first ending theme to the 2012 variety showKoekita!!; "Nexus" was the opening theme of the Ore no Imōto ga Konna ni Kawaii Wake ga Nai Portable ga Tsuzuku Wake ga Nai video game, as well as the theme for the ninth volume of the Oreimolight novels; "Connect" was used as the opening theme to the 2011 anime television series Puella Magi Madoka Magica; and "Naisho no Hanashi" was the ending theme to the 2012 anime television series Nisemonogatari.