Mesulergine () (developmental code name CU-32085) is a drug of the ergoline group which was never marketed.
Mesulergine acts on serotonin and dopamine receptors. Specifically, it is an agonist of dopamine D<sub>2</sub>-like receptors and serotonin 5-HT<sub>6</sub> receptors and an antagonist of serotonin 5-HT<sub>2A</sub>, 5-HT<sub>2B</sub>, 5-HT<sub>2C</sub>, and 5-HT<sub>7</sub> receptors. It also has affinity for the 5-HT<sub>1A</sub>, 5-HT<sub>1B</sub>, 5-HT<sub>1D</sub>, 5-HT<sub>1F</sub>, and 5-HT<sub>5A</sub> receptors.
Mesulergine had entered clinical trials for the treatment of Parkinson's disease; however, further development was halted due to adverse histological abnormalities in rats. It was also investigated for the treatment of hyperprolactinemia (high prolactin levels).