Alfred Lebbeus Loomis (1831 – 1895) was an American physician who served as president of the Association of American Physicians.
He was born at Bennington, Vermont. He graduated from Union College in 1851, studied medicine at the College of Physicians and Surgeons, New York, and graduated in 1852. At this time the science of auscultation and percussion was developing very rapidly, and this circumstance led him to adopt diseases of the lungs and heart as his specialty. He was appointed visiting physician to Bellevue Hospital in 1859, and became lecturer on physical diagnosis at the College of Physicians and Surgeons in 1862.
Shortly after this Loomis's health broke down completely, and he spent six months in the Adirondacks. The benefit derived from his residence there led to the establishment, years later, of Dr. Edward Livingston Trudeau's Adirondack Cottage Sanitarium at Saranac, and also, at Liberty, Sullivan Co., N. Y., of a Hospital for Consumptives. In 1866 Loomis became professor of the theory and practice of medicine at the University of the City of New York, the medical department of which later became University and Bellevue Hospital Medical College. Professor Loomis was appointed visiting physician to Mount Sinai Hospital in 1874.