Δ-11-Tetrahydrocannabinol (Delta-11-THC, Exo-THC, Δ11-THC, Δ9(11)-THC, exo-Tetrahydrocannabinol) is a rare isomer of tetrahydrocannabinol, developed in the 1970s.

In recent studies in 2022 it was found to "significantly reduce" the effects of Δ9-THC and has been suggested as antagonist of the CB1 receptor in humans, with the cited study showing "one partial success in the quest for an antagonist is the fact that D9,11-THC was found to significantly reduce the effect of D9-THC.

"[4][5] and did not substitute for THC in rhesus monkeys.

[6][7] It has been identified as a component of grey market vaping liquids sold for use in humans.

[8] Exo-THC has been identified as an impurity found in pharmaceutical Dronabinol.