Penicillin is obtained from fungi, specifically a group of molds known as Penicillium. The discovery of penicillin, one of the first widely used antibiotics, is credited to Sir Alexander Fleming in 1928. Fleming observed that the mold Penicillium notatum produced a substance that could inhibit the growth of bacteria. This substance was later named penicillin and became a groundbreaking antibiotic in the field of medicine, revolutionizing the treatment of bacterial infections. Therefore, the correct answer is (B) Fungus.