Infest the Rats' Nest's first single, "Planet B", was given a surprise release on 8 April 2019, before the release of the band's fourteenth studio album Fishing for Fishies, along with an accompanying music video. The song not being featured on the track list for Fishing for Fishies as well as its distinct contrast to the sounds on that album led to speculation that the band might release a second album in 2019.

During a Reddit AMA on 30 April, the band confirmed the next album was in the works and would include "Planet B", but they had not decided if it would be released in 2019. The album was initially believed to be named Auto-Cremate due to the band's use of the name as their username in the AMA, but was later confirmed to be titled Infest the Rats' Nest.

On 29 May, the band released the album's second single "Self-Immolate" with another accompanying music video a week after a teaser on social media. On 18 June, the band posted another teaser on social media which confirmed the album's title. The album was officially announced three days later with a release date of 16 August. On 25 June, the band released a third single, "Organ Farmer", along with a music video that included fans as extras.

Infest the Rats' Nest was composed and recorded mostly with only three of the band's usual seven-man lineup and showcases influences derived from heavy metal, mixing the band's signature garage rock guitar tones and psychedelic rock sounds with thrash metal. The album makes consistent use of double kick drumming influenced by heavy metal pioneers Motörhead. On the album's themes, frontman Stu Mackenzie explained that the A-side is about current problems, especially ecological disaster, and is set in the near future, and the B-side is about the story of a group of rebels attempting to settle on Venus after being forced to leave Earth. Mackenzie also said that the album's strong thrash metal influence was derived from bands such as Metallica, Slayer, Exodus, Overkill, Sodom, Rammstein and Kreator.

TRACKLIST

1. King Gizzard And The Lizard Wizard;King Gizzard & The Lizard Wizard - Planet B
2. King Gizzard And The Lizard Wizard;King Gizzard & The Lizard Wizard - Mars For The Rich
3. King Gizzard And The Lizard Wizard;King Gizzard & The Lizard Wizard - Organ Farmer
4. King Gizzard And The Lizard Wizard;King Gizzard & The Lizard Wizard - Superbug
5. King Gizzard And The Lizard Wizard;King Gizzard & The Lizard Wizard - Venusian 1
6. King Gizzard And The Lizard Wizard;King Gizzard & The Lizard Wizard - Perihelion
7. King Gizzard And The Lizard Wizard;King Gizzard & The Lizard Wizard - Venusian 2
8. King Gizzard And The Lizard Wizard;King Gizzard & The Lizard Wizard - Self-Immolate
9. King Gizzard And The Lizard Wizard;King Gizzard & The Lizard Wizard - Hell