Infest the Rats' Nest is the fifteenth studio album by Australian psychedelic rock band King Gizzard & the Lizard Wizard.

[2] During a question-and-answer on 30 April with fans on Reddit, the band confirmed the next album was at an early stage of production and would include "Planet B", but they had not decided if it would be released in 2019.

[8] On August 13, the band released Mars For The Rich, a first-person shooter browser game named after and featuring the album's starting track.

[13][14][15] The group had experimented with heavy music in previous releases such as Nonagon Infinity, but Infest the Rats' Nest marked a deeper exploration of the style.

[1] "Superbug" has been described as a more downtempo stoner rock or sludge metal song than the rest of the track listing, and has been compared to the work of Sleep or Melvins.

[14] On the album's lyrical themes, frontman Stu Mackenzie explained that the A-side is about contemporary issues such as ecological disaster and climate change and is set in the near future, and the B-side follows a group of rebels attempting to colonise Venus after being forced to leave Earth.

[24] In his review for AllMusic, writer Tim Sendra concluded that "King Gizzard aren't sugarcoating anything, either musically or thematically, and that makes for their most timely and political album yet.

"[25] Stuart Berman in Pitchfork commended the album as the band's "most succinct and single-minded statement to date" and its themes and heavy metal performances, but also said that it was "lacking both the unpredictable detours of their biggest rock-outs and the insidious melodies of their more pop-focused work.

"[11] A three out of five star NME review by Danii Leivers highlighted "Planet B" as a standout and compared it to Master of Puppets-era Metallica, but noted "as the album reaches its mid-section, the material does start to wear thin" and that not all of the tracks were memorable or cohesive.

[20] In PopMatters, Callum Bains described Infest the Rats' Nest as "a brutal, fear-inducing harbinger of our impending existential doom as the band steps on the soapbox to paint the apocalyptic horror of the climate emergency".

[1] In Consequence, William Ruben Helms praised the musical performances and dark lyrical themes, and concluded that "while it feels like a minor misstep in comparison to much of their catalog, it finds the band crafting forceful and ferocious, mosh pit-friendly rippers that are politically and socially relevant.