Repentless is the twelfth and most recent[1][2] studio album by American thrash metal band Slayer, released on September 11, 2015.

When asked in May 2011 if Slayer was going to make a follow-up to World Painted Blood (2009), then-Slayer drummer Dave Lombardo replied that, although nothing had been written yet, there were "definitely plans.

[6] On February 20, 2013, it was announced that Lombardo would not take part in Slayer's Australia tour due to contractual disputes, and his place would be taken by former drummer Jon Dette.

[7] Being interviewed in late February by Soundwave TV, guitarist Kerry King elaborated more on the personnel status for the album.

Lombardo's permanent replacement was later announced to be Paul Bostaph,[9] who was previously the band's drummer from 1992 to 2001, appearing on several albums.

[12] King had announced his desire for the band to continue, but Araya was more uncertain, stating, "After 30 years, it would literally be like starting over," and expressing doubts that Slayer's fanbase would approve of such a change.

[17] King later said that he and Lombardo had been working on music prior to the holidays and that they had completed three songs, in addition to three outtakes from the previous record.

"[23] Araya announced that the band would start writing the new album upon completion of the 2012 Mayhem Festival tour, which ended in August of that year.

[24] Since their recorded songs still needed to be mixed, King announced in a late August 2012 interview that there had been a twelve-day window where the band had been able to "hijack Greg Fidelman from Metallica" for further production on the album.

[25] In February 2013 during an interview with Eddie Trunk, King declared that, while Hanneman still had not been involved with the album, the band was waiting for label issues to be resolved before recording.

[31] King further revealed that he and drummer Paul Bostaph have recorded 11 songs on a demo, while also working on some additional tracks, seven of which had complete lyrics.

[32] On April 24, 2014, Slayer offered a free download of "Implode,"[33] their first song in five years as well as their first recording to feature Holt on guitar.

[40] On September 3, 2015, a behind the scenes mini-documentary looking at the making of the music video for the album's title track was released by Rolling Stone.

[54] Repentless sold 49,000 copies in its first week and debuted number four on the US Billboard 200, the band's highest position in its native country.

Writing for Exclaim!, Greg Pratt said that Repentless "isn't going to be one of the classic Slayer albums, but there's still plenty of good thrash to be found.

"[46] Journalist J.C. Maçek III of Spectrum Culture wrote "The truth is that it might be easy to dismiss Slayer after almost 35 years as a nostalgic metal act.

"[58] AllMusic writer Thom Jurek gave the album three out of five stars, calling Repentless "a retro, workmanlike effort from a band determined to soldier on, and that's fine.

"[43] The Guardian stated that "Slayer have always been a model of consistency and a band that fans of vicious, vein-bursting heavy metal can rely on.

"[47] Kim Kelly, writing in Spin was less enthusiastic, calling the album "middling" and stating that it "mostly falls flat.