NDTDI, also known as 8,10-seco-LSD, is a tricyclic tryptamine derivative which is thought to act as a serotonin receptor agonist, though its pharmacology has not been studied in detail. It is a structurally simplified analogue of the psychedelic drug lysergic acid diethylamide (LSD) and is reported to retain similar effects, though with many times lower potency. NDTDI is specifically the analogue of LSD in which the carbon atom at position 9 of the ergoline ring system has been removed. It has been sold as a designer drug since 2016 and was first identified by a forensic laboratory in Slovenia in 2017. NDTDI was made illegal in Latvia in March 2017.

The simplified analogue of NDTDI and LSD in which the carbons at positions 9 and 10 of the ergoline ring system have been removed, resulting in a fully non-rigid tryptamine derivative, is N-DEAOP-NMT.