Testament is an American thrash metal band from Berkeley, California. Formed in 1983 under the name Legacy, the band's current lineup comprises rhythm guitarist Eric Peterson, lead vocalist Chuck Billy, lead guitarist Alex Skolnick, bassist Steve Di Giorgio and drummer Dave Lombardo. Testament has experienced many lineup changes over the years, with Peterson being the only remaining original member, though they have since been rejoined by one of its songwriters Skolnick, who had been out of the band from 1992 to 2005. Billy has been a member of Testament since 1986, when he replaced original singer Steve "Zetro" Souza, who had joined Exodus as the replacement of Paul Baloff. He and Peterson are the only members to appear on all of Testament's studio albums, with the latter being the only constant member overall.

Labeled as one of the "big six" of the 1980s Bay Area thrash metal scene (along with Exodus, Death Angel, Lååz Rockit, Forbidden and Vio-lence), Testament is often credited as one of the most popular and influential bands of the thrash metal scene, as well as one of the leaders of the second wave of the genre in the late 1980s. They have also been referred to as one of the "big eight" of thrash metal, along with Metallica, Megadeth, Slayer, Anthrax, Exodus, Overkill and Death Angel. The band has sold over 1.4 million albums in the United States since the beginning of the SoundScan era and over 14 million copies worldwide. To date, Testament has released thirteen studio albums (one of which is a collection of re-recorded songs), four live albums, five compilation albums, twelve singles and three DVDs.

After signing to Atlantic Records in 1986, and changing its name from Legacy to Testament, the band released their debut album The Legacy in 1987, followed a year later by The New Order (1988); both albums were acclaimed by critics and the press, including heavy metal-related publications. The band achieved mainstream popularity with its third album Practice What You Preach (1989), which was Testament's first album to climb up the Top 100 on the Billboard 200 chart. A string of more successful albums were released during the early-to-mid-1990s, including Souls of Black (1990), The Ritual (1992) and Low (1994), with the first two also entering the Top 100 on the Billboard 200 chart. After Atlantic dropped the band in 1995, Testament (who had at this point had begun to experiment with a death metal-influenced sound) continued to record and perform until their temporary hiatus in 2001, when Billy was diagnosed with cancer. By 2005, his cancer was in remission and Testament had resumed activity, which saw a brief reunion of The Legacy lineup, resulting in the live album Live in London. Since then, Testament has experienced a resurgence of popularity, with four of their studio albums—The Formation of Damnation (2008), Dark Roots of Earth (2012), Brotherhood of the Snake (2016) and Titans of Creation (2020)—all entering the Top 100 on the Billboard 200, and they have continued to tour consistently. The band is currently working on new material for their fourteenth studio album, which is tentatively due for release in 2023.