Forestella (Korean: 포레스텔라) is a South Korean crossover male vocal quartet formed through the JTBC singing competition Phantom Singer 2, which aired in 2017. They won first place on the show and officially debuted on March 14, 2018, with the album Evolution. Since their debut, they have released another two studio albums and gained public recognition for their performances on Immortal Songs: Singing the Legend, festivals and other televised concerts. They appeared in a total of ten episodes on Immortal Songs special King of Kings. They competed in a total of eight episodes. They lost two episodes at first but then won six consecutive episodes, which is considered as an absolute record in the show's history. Because of that record, they were invited as a special guest for celebratory performances in the 2023, 2024, and 2025 King of Kings Specials.

The quartet was formed through the second season of the singing competition Phantom Singer. Cho Mingyu, Ko Woo-rim, Bae Doo-hoon, and Kang Hyung-ho each separately auditioned for the competition. During the competition, Cho Mingyu selected Ko Woo-rim for the 2nd round competition and trained him. Then, he selected Bae Doo-hoon for the 3rd round competition to add variety to the team color. In the final competition, Kang Hyung-Ho joined the team. Cho Mingyu got the nickname "Strategist" during the competition because he meticulously considered each contestant's timbre and whether they would match his voice before selecting them. The quartet prior to the finals named themselves "Forestella", which is a portmanteau of "forest" and "stella" (Italian: star). As the winning group, they won prize money as well as an exclusive contract with Arts & Artists, which manages some of the country's preeminent classical musicians, to promote together for a year.

Bae is a musical actor who had studied acting at the Korea National University of Arts and occasionally sang for Aux, a gugak-rock fusion band. He appeared in Hidden Singer and The Voice of Korea prior to auditioning for Phantom Singer. Cho and Ko are the only classically-trained singers of the quartet and are alumni of Seoul National University's famed College of Music. Cho had been planning to continue with graduate studies in Germany and was a member of the Seoul Metropolitan Opera for several years. Ko was then a third-year undergraduate voice major who had been a finalist and semi-finalist in several vocal competitions. Kang was the only member without any formal training in either music or the performing arts, although he was the vocalist of an amateur rock band he and some friends had formed as college students. He was a chemical engineer and researcher at Lotte and took a temporary leave of absence to audition, eventually resigning about a year after Forestella debuted.

While on Phantom Singer 2, the members already differentiated themselves from other contestants for their willingness to experiment with other genres and for their "adventurous" song selections, a reputation which persists to this day. Bae, Cho and Ko had been grouped together in the same team during the first quartet stage and were the first team to perform a rock song, Imagine Dragons's "Radioactive", in its original style rather than rearranging it. Kang, despite his background as a vocalist in a rock band, had demonstrated his versatility performing various genres with other contestants. As Forestella, they surprised viewers with a tango-pop rock arrangement of Claudio Baglioni's "Come Un Eterno Addio" during the second final stage.

Forestella debuted on March 14, 2018, with the full-length album Evolution, which was praised by critics for showcasing the members' vocal abilities and reinterpretations of songs from a wide spectrum of genres. They held a series of concerts in Seoul before embarking on a nationwide tour in nine cities. After their tour ended, they held a series of joint concerts with Forte di Quattro, winners of the first season of Phantom Singer. During the latter half of the year, they gained further public recognition through their appearances on the KBS singing show Immortal Songs: Singing the Legend, especially after winning Episode 374, their first win on the show.

In Episode 392 of Immortal Songs, which aired on February 23, 2019, the group covered "Bohemian Rhapsody" and the video of their performance uploaded by KBS went viral among both domestic and international fans, spawning numerous reaction videos. They caught the attention of Secret Garden who collaborated with them to record a Korean-language remake of "Beautiful". The song was pre-released as a digital single by Secret Garden and later included in the South Korean and Japanese releases of their album Storyteller.

On May 22, 2019, Forestella released their second full-length album Mystique, to both critical and popular acclaim. One of the tracks, "Dear Moon" (달하 노피곰 도다샤), was released as a promotional digital single two weeks prior and was based on a Baekje-era poem entitled "Jeongeupsa" (정읍사). It was one of the best-selling albums in the domestic classical charts, becoming certified "platinum" by December, and they became only one of three classical artists to have an album sell more than the "gold" certification that year.

In September 2019, the group decided to continue promoting together and renewed their group contract. Cho and Bae joined other agencies for their solo activities. Bae returned to musical theater while Cho and Kang both released songs as solo artists; Cho's first single album Shinsegae: New Age was released on February 16, 2020, while Kang released a single titled Universe on October 29, 2020. Ko opted against a solo career in favor of continuing his studies, although he has performed at various classical recitals and concerts.