Martin Kulldorff (born 1962) is a Swedish biostatistician. He was a professor of medicine at Harvard Medical School from 2003 until his dismissal in 2024. He is a member of the US Food and Drug Administration's Drug Safety and Risk Management Advisory Committee and a former member of the Vaccine Safety Subgroup of the Advisory Committee on Immunization Practices at the Centers for Disease Control and Prevention.

In 2020, Kulldorff was a co-author of the Great Barrington Declaration, which advocated lifting COVID-19 restrictions on lower-risk groups to develop herd immunity through infection before vaccines became available, while promoting the fringe notion that vulnerable people could be simultaneously protected from the virus. The declaration was widely rejected, and was criticized as being unethical and infeasible by Tedros Adhanom Ghebreyesus, the director-general of the World Health Organization. Francis S. Collins, N.I.H. director, called him a "fringe epidemiologist".

During the pandemic, Kulldorff opposed disease control measures such as vaccination of children, lockdowns, contact tracing, and mask mandates.

Kulldorff was born in Lund, Sweden, in 1962, the son of Barbro and Gunnar Kulldorff. He grew up in Umeå and received a BSc in mathematical statistics from Umeå University in 1984. He moved to the United States for his postgraduate studies as a Fulbright fellow, obtaining a doctorate in operations research from Cornell University in 1989. His doctoral thesis, titled Optimal Control of Favorable Games with a Time Limit, was written under the direction of David Clay Heath.

Kulldorff was an associate professor at the Department of Community Medicine at the University of Connecticut for five years and an associate professor at the Department of Statistics at Uppsala University for six years. He has also worked as a scientist at the National Institutes of Health in the US. From 2003 to 2021 he was a professor of medicine at Harvard Medical School, and from 2015 to 2021 he was also a biostatistician at the Brigham and Women's Hospital.

With Farzad Mostashari, Kulldorff developed SaTScan, a free software program used for geographical and hospital disease surveillance which is widely used, as well as a TreeScan software program for data mining. He is the co-developer of the R-Sequential software program for exact sequential analysis. He helped develop and implement statistical methods used by the Vaccine Safety Datalink (VSD) project that the CDC uses, among other tools, to discover and evaluate vaccine health and safety risks.

During the COVID-19 pandemic, Kulldorff advised Florida governor Ron DeSantis on health policy. In a September 2020 meeting he advocated aiming for herd immunity by not inhibiting the virus, saying that young people could "live normal life" until it had been reached, at which point older people could live more normal lives too. and co-authored the Great Barrington Declaration.

In 2021, Kulldorff was named a senior scientific director at the Brownstone Institute, a right-wing think tank launched by Jeffrey Tucker that publishes articles challenging various measures against COVID-19, presenting research supporting authors' opinions, and discussing alternative measures. Jay Bhattacharya and Sunetra Gupta, his co-authors on the Great Barrington Declaration, also have had roles there. Tucker is the former editorial director of the American Institute for Economic Research (AIER), where the declaration was signed.