René Gerónimo Favaloro (July 12, 1923 – July 29, 2000) was an Argentine cardiac surgeon and educator best known for his pioneering work on coronary artery bypass surgery using the great saphenous vein.

Favaloro was born in 1923 and raised in La Plata; his grandparents were Sicilians from the island of Salina.

The surname Favaloro is derived from the Sicilian word Favaloru, referring to one who grows or sells beans; the term can also be used to denote a scrounger.

In 1936, Favaloro was admitted into the Colegio Nacional de La Plata. After graduating from high school, he was admitted to the School of Medicine at the National University of La Plata. During his third year, he began his medical residency at the Hospital Policlínico San Martín, a medical center that received the most complicated cases from much of Buenos Aires province. This residency brought him into contact with patients for the first time. He attended procedures carried out by professors José María Mainetti and Federico E. B. Christmann, from whom he learned the simplicity and standardization that he would later apply to cardiovascular surgery, one of his many great contributions to cardiovascular operating techniques. Favaloro graduated with a medical degree in 1949.

He then applied for a position as a medical auxiliary, but the offer required him to enroll in the Peronist Party, which he did not accept. He moved instead to a small town named Jacinto Aráuz in La Pampa Province after being offered a job as the town's doctor; when the resident doctor died, he succeeded him and brought his brother Juan José into the clinic. He married María Antonia Delgado in 1951.

Favaloro and his brother endeavored to improve the general level of health in what was then a remote region. They trained and educated the general public, teachers, and nurses and improved health-care delivery. They equipped the town with an operating room and X-ray and improved the laboratory, thereby providing essential surgical and diagnostic tools.^{[citation needed]}

Favaloro became interested in developments in cardiovascular intervention, and developed an enthusiasm for thoracic surgery. During a visit to La Plata, he met Professor José María Mainetti, who pointed him in the direction of the Cleveland Clinic. Although in the beginning he had doubts about leaving his profession as a rural physician, he thought that he could make a greater contribution to the community on returning from the United States. With few resources and rudimentary English, he decided to travel to Cleveland. He first worked as a resident and later as a member of the surgical team, working with Donald B. Effler, head of cardiovascular surgery, F. Mason Sones, Jr., who was in charge of the Angiography Laboratory, and William L. Proudfit, head of the Department of Cardiology.

In the beginning, the major part of his work involved valvular and congenital diseases; later on, he became interested in other areas. Every day, having hardly finished working in the operating room, Favaloro would spend hours and hours reviewing coronary angiograms and studying coronary arteries and their relation with the cardiac muscle. The laboratory of Sones, father of the coronary angiography, had the largest collection of angiograms in the United States.