B1A4 (Korean: 비원에이포) is a five member South Korean boy band founded by WM Entertainment in 2011. The band consists of Jinyoung (leader), Baro, Gongchan, Sandeul, and CNU (Shin Woo). They have gained much interest due to being first introduced in a webtoon and for their unique sound mixing pop with rock for their debut album. Their group name, B1A4, has been explained as being due to one member having B blood type, and the other four having A blood type. It also stands for "Be The One, All For One".

Biography B1A4 debuted on April 21, 2011 with their debut track 'O.K' off of their album 'Let's Fly' and released a music video. They were first introduced to the world through the creative marketing of webtoons before their actual pictures were released. Their debut album 'Let's Fly' includes a song written and composed by the leader Jinyoung. As rookies, this garners much interest being that most debut albums contain little input from the members. They made their live debut on April 23, 2011 on MBC's Music Core. Over the week of May 1st, 2011, they were a guest on Starry Night radio.