Inclusion Criteria:  Age 30 to 65 Comfortable speaking and writing in English Diagnosis of Bipolar Disorder II with current depression Have a care partner/support person available throughout the study Able to attend all in-person visits at UCSF as well as virtual visits Having tried at least two previous medication trials for their bipolar disorder, each lasting at 6 weeks or more. Have an established mental health care provider who is seen at least twice a month  Exclusion Criteria:  Current or previous diagnosis of Bipolar I Disorder History of schizophrenia spectrum or psychotic disorder Use of psychedelics within the past 12 months, including MDMA and Ketamine Current diagnosis of cancer Seizures that continue to the present Fear of blood or needles Regular use of medications that may have problematic interactions with psilocybin, including but not limited to antidepressants (Bupropion allowed), serotonin antagonists, some antipsychotics, dopamine agonists/antagonists, stimulants, opioids, and Lithium. A health condition that makes this study unsafe or unfeasible, determined by study physicians