Barry J. Marshall AC, FRACP, FRS, FAA is an Australian physician and microbiologist best known for his discovery of Helicobacter pylori (H. pylori) and its role in gastric diseases, including peptic ulcers and gastric cancer. In the early 1980s, alongside Robin Warren, he challenged the prevailing belief that ulcers were caused by stress and lifestyle, proving instead that H. pylori infection was the primary culprit. To demonstrate his theory, Marshall famously drank a culture of H. pylori, developed gastritis, and successfully cured himself with antibiotics. This groundbreaking discovery revolutionized gastroenterology and led to effective treatments, benefiting millions worldwide. In 2005, he and Warren were awarded the Nobel Prize in Physiology or Medicine for their pioneering work. His work has significantly impacted global healthcare, particularly in high-prevalence regions like East Asia, reducing the burden of gastric ulcers and gastric cancer. As a fellow of the Royal Society (FRS) and other prestigious institutions, Marshall remains at the forefront of infectious disease research, advancing new approaches to improve gastrointestinal health worldwide.