1P-LSD or 1-propionyl-lysergic acid diethylamide is a psychedelic drug of the lysergamide class that is a derivative and functional analogue of LSD and a homologue of ALD-52. It has been sold online as a designer drug since 2015.^{[1][2][3][4][5][6]} It modifies the LSD molecule by adding a propionyl group to the nitrogen molecule of LSD’s indole.