Gerhard Armauer Hansen was a Norwegian physician born on July 29, 1841. He is best known for discovering the bacterium Mycobacterium leprae, which causes leprosy. His work in the 1870s helped to identify the disease's infectious nature, leading to better understanding and treatment. Hansen's research laid the foundation for modern leprosy studies and public health initiatives. He was also involved in advocating for the humane treatment of individuals affected by leprosy, emphasizing the importance of compassion and care. His contributions significantly advanced the medical community's approach to this historically stigmatized disease.