Morning Musume '21 (モーニング娘。 '21, Mōningu Musume Two-One.), formerly simply Morning Musume (モーニング娘。, Mōningu Musume.) and colloquially referred to as Momusu (モー娘。, Mōmusu.), are a Japanese girl group, holding the second highest overall single sales (of a female group) on the Oricon charts as of February 2012, with the Oricon record of most top ten singles with an amount of 64.
Morning Musume was formed in 1997 by rock singer-songwriter turned record producer Tsunku, who later composed the vast majority of the group's songs over the decade. They are the lead group of Hello! Project that specialises in upbeat, pop-oriented music coupled with dance performance. The group produced several splinter groups, and often collaborates with other Hello! Project acts, including Country Musume, Berryz Kobo, Cute, Melon Kinenbi, and v-u-den. The group's name can be translated as "Morning Girls" or "Morning Daughters"; as the name suggests, it consists of members mostly in their late adolescence and early 20s. The average age of the group members has remained more or less unchanged since its original formation because the group maintains a "school-like" system for their continuous line-up changes, with older members "graduating" and new, usually younger, members selected from nationwide auditions admitted to the group almost annually.