MDMB-FUBINACA (also known as MDMB(N)-Bz-F and FUB-MDMB) is an indazole-based synthetic cannabinoid that is a potent agonist for cannabinoid receptors and that has been sold online as a designer drug. The structure of MDMB-FUBINACA contains the amino acid, 3-methylvaline^{[citation needed]}, also known as l-tert-leucine. MDMB-FUBINACA has K_i values of 1.14nM at CB₁ and 0.1228nM at CB₂ and EC₅₀ values of 0.2668nM at CB₁ and 0.1411nM at CB_2.

There have been a large number of reported cases of deaths and hospitalizations in relation to this synthetic cannabinoid, mainly in Russia and Belarus. MDMB-FUBINACA was first reported in 2014 and quickly gained a reputation as the most deadly synthetic cannabinoid drug sold by 2015. Up to 700 hospitalisations and 25 deaths were initially linked to MDMB-FUBINACA in media and government reports, and subsequent testing confirmed that at least 1000 hospitalisations and 40 deaths had occurred as a consequence of intoxication by MDMB-FUBINACA as of March 2015.

In the United States, MDMB-FUBINACA is a Schedule I controlled substance.

As of October 2015, MDMB-FUBINACA is a controlled substance in Belarus, Russia, and China.

In July 2021, it was included in Table II-A in the list of prohibited drugs of Portugal.^{[citation needed]}