Médecins Sans Frontières (MSF) (pronounced [medəsɛ̃ sɑ̃ fʁɔ̃tjɛʁ] ( listen)), or Doctors Without Borders, is a secular humanitarian-aid non-governmental organization best known for its projects in war-torn regions and developing countries facing endemic diseases. Its headquarters are in Geneva, Switzerland. The organization is known in most of the world by its French name or simply as MSF, but in Canada and the United States the name Doctors Without Borders is commonly used. In 2007 over 26,000, mostly local, doctors, nurses and other medical professionals, logistical experts, water and sanitation engineers and administrators provided medical aid in over 60 countries. Private donors provide about 80% of the organization's funding, while governmental and corporate donations provide the rest, giving MSF an annual budget of approximately US$400 million.

Médecins Sans Frontières was created in 1971 by a small group of French doctors and journalists in the aftermath of the Biafra secession, who believed that all people have the right to medical care regardless of race, religion, creed or political affiliation, and that the needs of these people outweigh respect for national borders.