13-Fluorolysergol, specifically as the (+)-enantiomer (+)-13-fluorolysergol, is a selective serotonin 5-HT_2A receptor weak partial agonist or antagonist of the ergoline family. It is highly selective for activation of the serotonin 5-HT_2A receptor over the serotonin 5-HT_2B and 5-HT_2C receptors (EC₅₀Tooltip half-maximal effective concentration = >10,000 nM). (+)-13-Fluorolysergol has relatively weak maximal efficacy in activating the serotonin 5-HT_2A receptor (E_maxTooltip maximal efficacy = 17%). It is a derivative of lysergol.