2-Oxo-LSD, also known as 2-oxy-LSD or 2-keto-LSD, or more fully as 2-oxo-2,3-dihydro-LSD, is a lysergamide and metabolite of the psychedelic drug lysergic acid diethylamide (LSD). It is a metabolite of LSD in both humans and various animal species, although there are important differences in LSD metabolism and relative proportions of metabolites between species.

It is formed directly from LSD in the body and is also possibly an intermediate in the generation of LSD's major metabolite 2-oxo-3-hydroxy-LSD (O-H-LSD), which is present in urine at concentrations 4 to 40 times those of LSD in humans. However, O-H-LSD may also form from other metabolites, such as 3-hydroxy-LSD. The specific enzymes responsible for the generation of individual LSD metabolites like 2-oxo-LSD are largely unknown. However, several cytochrome P450 enzymes were investigated and implicated in the formation of O-H-LSD in 2019.

2-Oxo-LSD showed absence of various pharmacological effects in animals. In contrast to LSD and certain other metabolites like 13-hydroxy-LSD, 2-oxo-LSD failed to produce LSD-like electroencephalogram (EEG) changes in rabbits. 2-Oxo-LSD at a dose of 300 μg orally produced no psychoactive effects in a human subject who had previously responded to 30 μg LSD. It was concluded that 2-oxo-LSD shows no LSD-like activity in the central nervous system and hence is inactive. 2-Oxo-LSD's derivative O-H-LSD showed profound loss of activity at the serotonin 5-HT₂ receptors compared to LSD in vitro. 2-Oxo-LSD is said to readily enter the brain.

2-Oxo-LSD was first described in the scientific literature by Julius Axelrod and colleagues in 1957.