Theodor Albrecht Edwin Klebs (6 February 1834 – 23 October 1913) was a German-Swiss pathologist. He is mainly known for his work on infectious diseases. His works paved the way for the beginning of modern bacteriology, and inspired Louis Pasteur and Robert Koch. He was the first to identify a bacterium that causes diphtheria, which was called Klebs–Loeffler bacterium (now Corynebacterium diphtheriae). He is the father of physician Arnold Klebs.