Onyanko Club (おニャン子クラブ, Onyanko Kurabu; "Kitty Club") was a large all-girl Japanese pop idol group in the 1980s. Some members of the group participated in spin-off groups, such as Nyangilas, Ushiroyubi Sasaregumi and Ushirogami Hikaretai. Many of the latter two groups' songs were used as theme songs of the popular 1980s anime series High School! Kimengumi and Tsuide ni Tonchinkan. Several big-name idols stemmed from the group; one of the best known being Shizuka Kudo. The group was produced by Hiroshi Ishida and Kazuji Kasai, both of whom were producers of Fuji TV's show Yūyake Nyan Nyan.

The group made its television debut on the first episode of Fuji TV's daily live television variety show "Sunset Meow Meow" (夕やけニャンニャン, Yūyake Nyan Nyan) on 1 April 1985. The show was aired from 5 p.m. to 6 p.m. Monday to Friday. In the beginning, the group consisted of nine high school girls and two high school graduates, namely Sayuri Kokushō (number 8) and Satomi Fukunaga (number 11). They were selected from participants in two special episodes of Fuji TV's weekly late-night show All Night Fuji. The two episodes entitled All Night Fuji: High School Girl Special (オールナイトフジ女子高生スペシャル, Ōru Naito Fuji Joshi Kōsei Supesharu) were produced as pilots of the show Yūyake Nyan Nyan and aired on 23 February and 16 March 1985. Yūyake Nyan Nyan had a segment where five candidates participated in a five-day long audition for becoming a new Onyanko Club member. Most of the Onyanko Club members except the first 11 members and other members who joined the group through the 1986 Miss Seventeen Contest were admitted to the group by winning the audition.

Every day since 15 April 1985, Tsurutarō Kataoka, a host of the program, had been provoking Dump Matsumoto, a female professional wrestler who is well known as a heel, by abusing her over the phone. On 19 April, while he was provoking her as usual, Matsumoto suddenly burst into the studio with a Shinai in her hand. Kataoka fled around the studio, then timidly repeated his apology to her. Seeing this, Onyanko Club members Sayuri Kokushō, Mika Nagoya, Satomi Fukunaga, and Sonoko Kawai broke into tears. This happening is considered one of the highlights of the program.

Less than three weeks from the launch of the show, six members were caught in photos taken by a photographer of tabloid magazine Shūkan Bunshun while they were hanging out and smoking in a kissaten (Japanese-style café) near Fuji TV's old headquarters in Shinjuku, Tokyo. They stopped appearing on the show from 18 April. Eventually, five of them were officially dismissed from the group without announcement as a result of underage smoking as of 25 April; one member was not smoking in the incident.

The group's debut single "Sailor Fuku o Nugasanai de" was premiered on Yūyake Nyan Nyan on 3 June. Lead vocalists (hereinafter referred to as "front vocals") for the single were Eri Nitta (number 4), Miharu Nakajima (number 5), Satomi Fukunaga (number 11) and Kazuko Utsumi (number 13). Released by Canyon Records on 5 July, the single debuted at number 34 on the Oricon's Japanese single chart (the national single chart) and peaked at number five in its sixth week of release in August. A day before the single's release date, a release and handshake event was scheduled at Sunshine City in Ikebukuro, Tokyo. The event was expected to have an attendance of about 500 people. However, over 4,000 people showed up at the site. As a result of reported injury and concerns over possible stampede, the event was canceled at the last minute before a scheduled start time.

In the same month, the group's member Sonoko Kawai (number 12) made her appearance as a supporting character in the episodes 11 and 12 of Fuji TV's live-action TV series Sukeban Deka. Subsequently, it was announced on Yūyake Nyan Nyan that Kawai's first solo single would be released in September. The single "Namida no Jasmine LOVE" and its B-side "Koi no Chapter A to Z" were premiered on Yūyake Nyan Nyan on 12 August and 19 August, respectively. The B-side features four Onyanko Club members as backing vocals: Sayuri Kokusho (number 8), Mika Nagoya (number 9), Mamiko Takai (number 16) and Sanae Jōnouchi (number 17). In late August, producers of the show Yūyake Nyan Nyan teamed up with producers of the live-action TV series Sukeban Deka and held a special audition on Yūyake Nyan Nyan to look for a new Onyanko Club member who would play a main character in a sequel to the TV series. The winner of the audition was Akie Yoshizawa, who was assigned number 25. A day before the release of Kawai's first single, a release event entitled "Nyan Touch Love Party" for the single was held at Yomiuri Land EAST in Inagi, Tokyo on 31 August.

Released by CBS/Sony Records on 1 September, Kawai's first single debuted at number five on the chart and topped the chart for the following two consecutive weeks. On 21 September, the group's first studio album Kick Off was released by Canyon Records. The album was directed by Hiroshi Watanabe (music producer) and contained 10 songs whose music was composed by several musicians, such as Jun Sato, Ken Takahashi, Etsuko Yamakawa, Kiyonori Matsuo and Tsugutoshi Goto, who all composed and arranged most of the group's and members' songs thereafter. All lyrics of the album were written by Yasushi Akimoto. The album reached number two on the Oricon's Japanese album chart and remained in the top 100 for 30 weeks. On 30 September, the group's first subgroup Ushiroyubi Sasaregumi made its television debut on Yūyake Nyan Nyan. Its members were Mamiko Takai and Yukiko Iwai (number 19).

The official fan club "Konyanko Club" run by Fujipacific Music was launched on 1 October. The number of fan club members peaked at about 190,000 during its operation. On 5 October, Onyanko Club had its first concert entitled "Kick Off" at Hibiya Yagai Ongakudo in Chiyoda, Tokyo. It was recorded and released as a video by Pony Inc. in the following month.