Beast Is the B2ST (Beast Is The Best) is the debut mini-album played by South Korean boy band Beast, and was released by Cube Entertainment on October 14, 2009. The songs were written and composed by Shin Sa-dong Tiger and Lee Sang-ho who have also produced songs for their labelmate, 4minute.

In October 2009, Beast held their debut showcase at the MTV GongGae Hall and made their live performance debut on KBS Music Bank with their debut single, "Bad Girl". A documentary recording the story of the group's debut titled MTV B2ST was filmed during this time, showing the members as they filmed their first music video and bonded with each other. Their debut mini-album, Beast Is the B2ST featured five songs, including the intro track "Beast Is the B2ST", "Mystery" and "Oasis". The song "Yet" (아직은, Ajigeun) was banned from airplay due to (believed) swearing in JunHyung's rap. This is actually quite a controversial topic among fans, seeing as some believe the "swear word" could have been another word entirely. Beast won their first award, Rookie of the Month for December, awarded by the Ministry of Culture, Sports and Tourism.

In early 2010, Beast promoted their second single, "Mystery", from the mini-album, with live performances on the weekly music shows. The members created their own humorous amateur music video for the song, featuring fellow Korean pop singers including members of Girls' Generation and Kara. The mini-album went on to sell 40,000 copies, an unusual feat for a Korean rookie group, with the album's original print run of 20,000 copies selling out in its first month.

On February 14, 2012, Beast's official YouTube channel uploaded a special music video for "Mystery". Beast first premiered this music video during their 'Beautiful Show' world tour concert in Seoul. The video was played in lieu of the group’s actual performance of the song, ending with the word “EASY” as the introduction to their next song in the lineup.

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