K3 is a Belgian-Dutch girl group with a Dutch-language pop repertoire, consisting of Hanne Verbruggen, Marthe De Pillecyn and Julia Boschman. In addition to music, they are also central to many films, television series and musicals. The signature style and iconicity of K3 rely on all three girls mostly wearing the same outfit, and they are traditionally a redhead, a brunette, and a blonde. Throughout its career, K3 has built a space within Dutch and Belgian pop culture, becoming one of the most successful groups of the Benelux. The group's name is derived from the first letters of the three first members from 1998: Karen Damen, Kristel Verbeke, and Kathleen Aerts.

Kathleen Aerts stepped out of the formation in March 2009. She was replaced by Josje Huisman later that year after winning the audition reality show K2 Zoekt K3. On 6 November 2015 Karen, Kristel and Josje were succeeded by Hanne Verbruggen, Klaasje Meijer and Marthe De Pillecyn after they became the winners of K3 Zoekt K3. In February 2021 Klaasje announced her departure from K3 and another audition reality show was held in the same year to find a new member. Of more than 22,000 participants, Julia Boschman won the contest and became part of the group.

The band was started by Niels William in 1997. It was first called Mascara and consisted of Karen Damen, Kristel Verbeke and Kelly Cobbaut. Their intention was to form a kind of Flemish version of the "Spice Girls". In 1998, Cobbaut left the group to go to college. She was supposed to be replaced by Deborah Ostrega, but she immediately withdrew after she signed the contract, because she didn't want to sing in Dutch. Ultimately, William managed to find Kathleen Aerts as a replacement and because again someone joined with a 'K' as the initial letter, they decided to change the name of the band to K3 on 13 November 1998. The first single was "Wat ik wil" (What I want). This release was not very successful.

In 1999, K3 participated in the selection for the Belgian entry for the Eurovision Song Contest with their song "Heyah Mama". The song was not well received by one of the judges, who called the girls "assorted meat products". Notwithstanding, "Heyah Mama" was released as a single and became the first big hit for the band, peaking at the number two spot of the Flemish Ultratop 50 chart, charting 25 weeks. Its popularity grew rapidly. About a year after becoming famous in Flanders, K3 also became famous in the Netherlands.

K3 is noted for being the first pop act to break through to the top of the charts without receiving any airplay from the regular music television channels. Their songwriters became Miguel Wiels, Alain Vande Putte and Peter Gillis.

In 2002, Niels William sold the band to Studio 100, a Flemish television production company for Dutch and Belgian programs, movies and musicals.

K3 provided many hits, they had released nine albums. Their eighth album Ya Ya Yippee sold more than 50,000 copies in pre-sales within the Benelux. The ninth album, Kusjes (Kisses), sold 20,000. They also released several DVD's with video clips, musicals, films and with specially recorded footage. K3 has a children's television program called De wereld van K3 (K3's World).

In 2006, a party was held at Plopsaland, a popular theme park, to celebrate the tenth anniversary of Studio 100. At the event, the band members opened the K3 Museum which provides an overview of their career. There are interviews, clothes, and props from the films to be seen, including the air scooters from the film K3 en het Magische Medaillon (K3 and the magic medallion). Their gold and platinum certifications can also be seen.