Bernard Lewinsky (born January 10, 1943) is a Salvadoran doctor and medical researcher. He is also a photographer, and many of his photographs are displayed at medical offices. He also organized a legal defense fund for his daughter Monica during an inquiry into her relationship with president Bill Clinton.

Lewinsky is a board certified radiation oncologist who is among the top 15% of breast cancer researchers in terms of proficiency of publication, according to Vitals.com. He is the President and owner of West Hills Radiation Therapy Center. Lewinsky is a Fellow of the American College of Radiology and also serves on the Medical Advisory Board of The Wellness Community Valley/Ventura, a cancer support organisation.

Lewinsky has studied non-surgical cancer treatments that aim to reduce the number of treatments that patients receive. He has also partnered with a veterinarian oncologist to help treat animals with cancer. Lewinsky has published a number of medical papers in collaboration with several other scientists that focus on "carcinoma of the breast". He has also been published in various textbooks.