11-Nor-9-carboxy-Δ9-tetrahydrocannabinol (11-COOH-THC or THC-COOH), often referred to as 11-nor-9-carboxy-THC or THC-11-oic acid, is the main secondary metabolite of tetrahydrocannabinol (THC) which is formed in the body after cannabis is consumed.

It is then metabolized further by conjugation with glucuronide,[2] forming a water-soluble congener which can be more easily excreted by the body.

[citation needed] Some jurisdictions where cannabis use is decriminalized or permitted under some circumstances use such tests when determining whether drivers were legally intoxicated and therefore unfit to drive, with the comparative levels of THC, 11-OH-THC and 11-COOH-THC being used to derive a "blood cannabis level" analogous to the blood alcohol level used in prosecuting impaired drivers.

11-COOH-THC is a Schedule 8 prohibited substance in Western Australia under the Poisons Standard (July 2016).

[15] Because 11-COOH-THC is substantially similar to the Schedule I controlled substance THC, possession or sale of 11-COOH-THC could be subject to prosecution under the Federal Analog Act.