Chthonic (styled as ChthoniC or ChThoniC) is a Taiwanese heavy metal band, formed in 1995 in Taipei. They have been called "the Black Sabbath of Asia." The group incorporates influences from traditional Taiwanese music, including adaptations of folk songs and the use of traditional instruments, most notably the erhu (often called the hiân-á [絃仔] in the band's native Taiwanese Hokkien). Their stated goal is to use their music to bring ancient history and mythology into the modern era especially to build awareness of the myths of Taiwan and tragic events in that country's history (for example, those experienced by the Seediq people).

Since 2011 their trademark erhu has been complemented with stringed instruments including the koto and shamisen, as well as Tibetan bells and shakuhachi and Seediq hunting flutes (Chinese: 獵首笛), the last of which are traditionally used by the indigenous people of Taiwan. The band members are also acclaimed artists and political activists who advocate independence for Taiwan and self-determination for Tibetans and Uighurs. Singer Freddy Lim served as Chairman of the Taiwan chapter of Amnesty International from 2010 to 2014 and has been a legislator since 2016, first representing the New Power Party before becoming an independent. Since their formation, Chthonic has released eight studio albums. The most recent of which, Battlefields of Asura, was released in October 2018.

Chthonic was formed in 1995, and the band name "Chthonic" is a Greek term referring to the earth and the underworld. In the west, the term is usually pronounced thonic. The original members were Freddy Lim and some of his classmates from high school and university. The line-up went through many changes before the band released their debut album in 1998. By that point the line-up had settled around Freddy Lim on vocals and erhu, Zac Chang on guitar, Xiao-Yu on bass, Xiao-Wang on drums, and Ambrosia on keyboards and backing vocals. Chthonic became quite popular in the rock scene in Taiwan. They played to a full house at Vibe, the main rock club in Taipei at the time, and played as headliners for large rock festivals like Spring Scream. They released their first single "Deep Plowing" ("深耕") in early 1998.

In their early years, Chthonic tried different styles of heavy metal. Lim sang clean vocals in "The Breath of Ocean" ("海息"); the early song "Cultivating" ("深耕") can be classified as power metal while "Decomposition of the Mother Isle (Aboriginal Gods Enthroned)" ("母島解體登基") is black metal. Keyboardist Ambrosia occasionally sang in the early songs as well. From the start, Lim has written songs in Taiwanese, Classical Chinese, and Mandarin Chinese; more recent albums have been released in English versions as well.

Chthonic's debut album, Where the Ancestors' Souls Gathered (祖靈之流), was released in late 1998. The band released the album independently and it reached No. 2 on the Tower Records pop music chart for Asia. In 1999 Zac, Xiao-Yu, and Xiao-Wang left the band and were replaced by Jesse Liu, Doris Yeh, and AJ Tsai respectively. The band recorded their second album 9th Empyrean (靈魄之界), which was released in Taiwan by Crystal Records in 2000. It reached No. 1 on the Tower Records pop music chart for Asia and was also considered one of the best ten Mandarin albums of that year by Hong Kong's MCB magazine.^{[citation needed]} This album's music style is closer to symphonic black metal, with Lim adopting harsh vocals mixed with keyboardist Ambrosia's female singing. The song "Guard the Isle Eternally" ("永固邦稷") was the first Chthonic song to mix Asian pentatonic scale melodies with black metal.

In 2000, Chthonic appeared at the Fuji Rock Festival, one of the biggest rock festivals in Japan, and embarked on their first international tour through Japan, Hong Kong, Malaysia, and Singapore. In Hong Kong, they signed with Catalyst Action Records, and in Japan, Soundholic was their distributor.

In 2001, keyboardist Ambrosia left the band and was replaced by Vivien Chen. Chthonic then recorded their third album, Relentless Recurrence, which was based on the legendary Taiwanese ghost story "Nâ-tâu-tsí--á [zh]." The album was recorded in Denmark and released in Taiwan by Crystal Records in 2002. The album retains the symphonic black metal style mixed with Taiwanese elements. Relentless Recurrence was also the first Chthonic album written entirely in Taiwanese. In 2002 the band completed their second international tour, and played at the old stadium of National Taiwan University with traditional Taiwanese lion drums and a traditional Taiwanese orchestra.

In 2002 Chthonic signed with Nightfall Records in the United States and released an English version of 9th Empyrean in North America. All subsequent Chthonic albums have been released internationally in English versions. In 2002 the band played festivals in the United States, Japan, and Hong Kong; and toured with Swedish black metal band Dark Funeral. In late 2002 keyboardist Vivien Chen left the band and was replaced by Luis Wei. In 2003 the band released the single "Satan's Horns," which was used as the theme song for the Taiwanese release of the movie Freddy vs. Jason. In 2003 they won the Best Band Award at the Taiwan Golden Melodies Award Ceremony.