Was penicillin discovered by accident?

Yes. In 1928, the Scottish research scientist Alexander Fleming found that mold had accidentally contaminated one of his experiments. The mold created a bacteria-free circle around itself, and Fleming deduced that the mold was an antibacterial agent that could kill many harmful bacteria. He named the active agent penicillin. By the middle of the twentieth century, Fleming’s discovery birthed a pharmaceutical industry that made synthetic penicillin to treat many bacterial diseases of the day, including syphilis, gangrene, and tuberculosis. He won the Nobel Prize in 1945 for his discovery.