Morning Musume's origins began with Sharam Q's auditions to find a female vocalist, broadcasted on ASAYAN. Although the winner was Heike Michiyo, band member Tsunku called back five of the finalists - Nakazawa Yuko, Ishiguro Aya, Iida Kaori, Abe Natsumi, and Fukuda Asuka - and proposed to them a challenge. If the five could sell 50,000 copies of their debut single, "Ai no Tane", in five days, they will be given a record deal, and their group is named Morning Musume. The challenge was completed, and the group began preparing for their major debut, starting with the single "Morning Coffee" in early 1998.
Not long after, Tsunku announced that three new members would be added to the group, and emerging from the auditions were Yasuda Kei, Yaguchi Mari, and Ichii Sayaka, known as the group's second generation. The group's debut album, First Time, was released, and was followed up by "Daite HOLD ON ME!", which became Morning Musume's first single to hit #1 on the Oricon charts.
1999 began with Morning Musume's first graduation, that of Fukuda Asuka, who decided to return to her studies. Now with only seven members, the group released two more singles, "Manatsu no Kousen" and "Furusato", which was followed by their second album, Second Morning. However, these releases performed poorly sales-wise, and so it was time to add in new members. Although the audition was expected to find two more members, only the young Goto Maki was chosen, and as an eight-piece group again, Morning Musume released their seventh single, "LOVE Machine". The single went on to sell over one million copies, becoming the group's best-selling single to date. Goto quickly became a fan favorite as well as a prominent face within the group.
The new millenium began with Ishiguro Aya's departure from the group, where she would pursue a career in fashion design. Although at seven members again, "Koi no Dance Site" was still a superb follow-up to "LOVE Machine", being the only other single to sell over one million copies. The follow-up album, 3rd -LOVE Paradise-, is also their best-selling original album to date. In the spring, four new members were added - Ishikawa Rika, Yoshizawa Hitomi, Tsuji Nozomi, and Kago Ai - known as the fourth generation. A month after the release of their CD debut, "Happy Summer Wedding", Ichii Sayaka graduated from the group, to pursue her own career in music.
The group's first single for the year, "Souda! We're ALIVE", became their third consecutive #1 single on the Oricon charts. That streak was broken by "Do it! Now", which only reached #3. Not surprisingly, it was the last single for Goto Maki, who graduated from the group in September to continue her solo career. However, the single "Koko ni Iruzee!" managed to reach #1. Near the end of the year, it was announced that Fujimoto Miki, a fellow solo artist in Hello! Project, would be added to Morning Musume's sixth generation. The Morning Musume LOVE Audition 2002 decided three more members to join Fujimoto, and they were Kamei Eri, Michishige Sayumi, and Tanaka Reina.
Although the sixth generation was announced at the beginning of 2003, they did not make their proper debut until Yasuda Kei's graduation in May. The single "Morning Musume no Hyokkori Hyoutanjima" was the group's first cover. After the group's fifth album, No.5, and the single "AS FOR ONE DAY", which reached #1 on the Oricon charts, Yasuda graduated from Morning Musume. This marked the time where Morning Musume had the most number of members, at sixteen before Yasuda's departure. Now at fifteen members, the sixth generation made their CD debut with the single "Shabondama". With so many members, Morning Musume had formed two "splinter" groups, known as Morning Musume Otomegumi and Morning Musume Sakuragumi, to promote activities separately and in smaller numbers. The year-end single "Go Girl ~Koi no Victory~" also coincided with the formation of Hello! Project's futsal team, Gatas Brilhantes H.P..
In 2004, after the release of the single "Ai Araba IT'S ALL RIGHT", Abe Natsumi graduated from Morning Musume to continue her solo career.
2005 opened with a new single, "THE Manpower!!!", and the graduation of Iida Kaori, which took place on January 30, 2005, at the conclusion of Hello! Project's winter tour. Yaguchi Mari became leader and Yoshizawa Hitomi became sub-leader. In February, the Morning Musume Lucky 7 Audition took place, where Tsunku described his search for an "ace" member that would represent the seventh generation. Surprisingly, no new members turned up, but after the follow-up Morning Musume Audition 2005, Kusumi Koharu was selected, and she was inducted into the group in May. Incidentally in April, Yaguchi was caught in a scandal, and in response, she left the group without a proper graduation, though the single "Osaka Koi no Uta" was still released even after this announcement. Yoshizawa became leader and Fujimoto Miki became sub-leader. Ishikawa Rika graduated from the group at the conclusion of their 2005 spring tour, and would continue on as the leader of v-u-den. Now with a ten-member line-up that included Kusumi, Morning Musume released their twenty-seventh single, "Iroppoi Jirettai".
In 2006, Morning Musume released their seventh original album, Rainbow 7, and followed up with their twenty-ninth single, "SEXY BOY ~Soyokaze ni Yorisotte~". During their spring tour, it was announced that Konno Asami and Ogawa Makoto would graduate from the group, both members to further pursue their studies. Konno graduated from Hello! Project on July 23, at the conclusion of Hello! Project's summer tour. During the month of August, the remaining Morning Musume members starred with v-u-den, Abe Natsumi, Tsuji Nozomi, Matsuura Aya, and Takarazuka Revue in Ribbon no Kishi The Musical, an adaptation of Tezuka Osamu's manga. Ogawa graduated at the end of its run on August 27, and took an indefinite hiatus from Hello! Project appearances. With only eight members in the line-up, the Morning Musume Happy 8ki Audition commenced, running from August to December. In that time, Morning Musume's thirty-first single, "Aruiteru", reached #1 on the Oricon charts, a title unachieved ever since "AS FOR ONE DAY" in 2003. At the end of the year, Mitsui Aika was added into the group, and at the 58th Kouhaku Uta Gassen, Morning Musume performed a medley with GAM.
2007 marked Morning Musume's tenth anniversary, and a special group was formed, named Morning Musume Tanjou 10nen Kinentai, to begin promotional activities throughout the year. Yoshizawa Hitomi's graduation was also announced. As spring season came about, Mitsui's CD debut was on the single "Egao YES Nude", and the group released their eighth original album, SEXY 8 BEAT. In March, Tsunku made a surprise announcement on Hello! Morning - two members from China, Junjun and Linlin, would be joining the eighth generation as "exchange students." Currently, those two are the only non-Japanese members to have been part of the group. After the release of the single "Kanashimi Twilight", Yoshizawa graduated on May 6, and Fujimoto Miki and Takahashi Ai took the positions of leader and sub-leader. However, no less than a month later, Fujimoto was caught in scandal - a scene quite parallel to Yaguchi Mari's departure two years back - and she left the group, in addition to taking a temporary hiatus from Hello! Project appearances following her spring concert tour with GAM. Takahashi and Niigaki Risa became leader and sub-leader, now fronting a line-up of nine, beginning with the single "Onna ni Sachi Are". In the autumn season, Morning Musume released their biggest singles compilation to date, a double album featuring all thirty-four singles, with the album covers being recreations of the covers for "Morning Coffee", their debut single, and "LOVE Machine", their best-selling single. The year was concluded with the release of the single "Mikan" and the appearance at the 58th Kouhaku Uta Gassen. Morning Musume performed a special medley with Berryz Kobo and °C-ute under the name "Hello Pro Wonderful All Stars". However, it was their last appearance on the show to date, thus breaking their consecutive ten-year streak.
Morning Musume released their first 2008 single, "Resonant Blue", and continued their 10th anniversary promotions with their spring concert tour, which had a set list containing all their singles to date. In addition to performing in Japan, the group had special stopovers in Shanghai, China and Seoul, South Korea, to further promote the expansion into Asia. For the summer season, Morning Musume collaborated with Takarazuka Revue again to perform Cinderella The Musical, an adaptation of Rogers and Hammerstein's musical with lyrics translated into Japanese. During the autumn season, the group began a series of tributes to legendary songwriter Aku Yuu. Takahashi and Niigaki portrayed Pink Lady in a special titled Hitmaker Aku Yuu Monogatari. The group's thirty-seventh single, "Pepper Keibu", was a cover of the famous Pink Lady song. To top it off, a tribute album titled COVER YOU was released, featuring covers of famous Aku Yuu-penned hits. 2008 marked the first year where there were no changes in Morning Musume's line-up.
2009 was a year teeming with activity. The group released their thirty-eighth single, "Naichau Kamo", and their ninth original album, Platinum 9 DISC. The album was followed up with the single "Shouganai Yume Oibito", which reached #1 on the Oricon charts. Its coupling track, "3, 2, 1 BREAKIN' OUT!", was the theme song for Anime Expo 2009 in Los Angeles, California, which Morning Musume attended as Guests of Honor and which marked their first performance in North America (not counting their fan club visits in Hawaii). The group's fortieth single, "Nanchatte Renai", reached #2 only to Hamasaki Ayumi's "Sunrise / Sunset ~LOVE is ALL~", but was an achievement in sales; selling over 70,000 copies, a feat unachieved since 2005. However, the year concluded with Kusumi Koharu's graduation from Hello! Project, which took place on December 6. "Kimagure Princess" was the last single to feature Morning Musume's most stable line-up.
2010 progressed almost like the year before. The eight-member Morning Musume released their forty-second single, "Onna ga Medatte Naze Ikenai", followed by their tenth original album, 10 MY ME, only a month later. In the spring, Morning Musume attended the Japan Expo 2010 in Paris, France, marking their first performance in Europe. The theme song for the event was "Tomo", the coupling track to their forty-third single "Seishun Collection", which in turn was the theme song for Morning Musume's musical during June, titled Fashionable. However, a surprising twist was made during the summer. Kamei Eri, Junjun, and Linlin would be graduating from Hello! Project, Kamei to tend to her atopic dermatitis and Junjun and Linlin to pursue careers in China. In turn, auditions commenced for the group's ninth generation, who would make their debut at the start of the new year. After another single, "Onna to Otoko no Lullaby Game", and another album, Fantasy! Juuichi, the triple graduation took place on December 15.
Morning Musume's ninth generation was introduced in January. Ikuta Erina, Sayashi Riho, and Suzuki Kanon were the winners selected from the audition, while Fukumura Mizuki made her debut from Hello! Pro Egg. However, only a week later, Takahashi Ai's graduation from Hello! Project was announced, to occur at the end of September. In turn, auditions commenced for Morning Musume's tenth generation. The ninth generation made their CD debut with the single "Maji Desu ka Ska!", which was followed by "Only you", and "Kono Chikyuu no Heiwa wo Honki de Negatterun da yo! / Kare to Issho ni Omise ga Shitai!", the final single for Takahashi. This line-up would still be featured on their twelfth original album, 12, Smart, released in October.
The tenth generation members were introduced on September 29th. Iikubo Haruna Ishida Ayumi Sato Masaki & Kudo Haruka were introduced the day before then leader Takahashi Ai graduated and appeared again in the final and gave their graduation messages to Ai and also sang with the existing members. Their addition makes the group stand at 12 members, the largest the group has been since 2005. Once Takahashi graduated, she passed leadership of both Morning Musume and Hello! Project to Niigaki Risa her fellow 5th generation member. This now makes Risa the longest serving member of the group and the 1st member to go from youngest in the group at entering to becoming leader.
On January 3, 2012, at the beginning of the Hello! Project 2012 Winter concert tours, Risa announced her graduation from Morning Musume and Hello! Project, to take place at the end of the 2012 Morning Musume Spring concert tour. Her leadership of Morning Musume will be passed on to Michishige Sayumi after she graduates. Risa stated that she originally planned to graduate at the same time as Takahashi Ai, but decided to stay for a while longer after the tenth generation members were introduced. It was suddenly announced on May 4, 2012 that Mitsui Aika would graduate from Morning Musume, but not Hello! Project, alongside Niigaki Risa at the end of the 2012 Morning Musume Spring concert tour due to worries over possible repeat injury to her ankle. On September 14th, the eleventh generation was announced and only one winner, Oda Sakura, was introduced. Tanaka Reina will graduate after the spring concert for Hello Project.