Dr. Andrew Posselt, a bariatric and transplant surgeon, is director of the Pancreatic Islet Transplantation Program at UCSF Medical Center. He specializes in adult and pediatric kidney, liver and pancreas transplantation, laparoscopic and open (traditional) bariatric surgery, robotic surgery and performed the first robotic donor nephrectomy at UCSF in May, 2023.

In addition to caring for patients, Posselt conducts research on pancreatic islet cell transplantation, a procedure that can allow people with type 1 diabetes to discontinue insulin therapy. He also investigates mechanisms by which a transplant recipient's body rejects or tolerates tissue from a donor who isn't genetically identical, and he studies the metabolic and biochemical consequences of bariatric surgery.

Posselt earned his medical degree and a doctorate in immunology from the University of Pennsylvania. He completed residencies in internal medicine and general surgery as well as a transplant fellowship at UCSF, before joining the staff in 2003.

Posselt is a member of several professional and honorary societies, and has given presentations on transplant issues related to patient care and research. At UCSF, he supervises residents and fellows in transplant services and general surgery.