Dimethylheptylpyran (1,2-dimethylheptyl-Δ³THC, DMHP, A-40824, EA-1476) is a synthetic analogue of THC, which was invented in 1949 during attempts to elucidate the structure of Δ⁹-THC, the active component of cannabis. DMHP is a pale yellow, viscous oil which is insoluble in water, but dissolves in alcohol or non-polar solvents.

DMHP is similar in structure to THC, differing only in the position of one double bond, and the replacement of the 3-pentyl chain with a 3-(1,2-dimethylheptyl) chain. It produces similar activity to THC, such as sedative effects, but is considerably more potent, especially having much stronger analgesic and anticonvulsant effects than THC, although comparatively weaker psychological effects. It is thought to act as a CB₁ agonist, in a similar manner to other similar cannabinoid derivatives.

DMHP and its O-acetate ester were extensively investigated by the US military chemical weapons program in the Edgewood Arsenal experiments, as possible non-lethal incapacitating agents.