Bjørn Lomborg (Danish: [ˈpjɶɐ̯ˀn ˈlɔmˌpɒˀ]; born 6 January 1965) is a Danish author, statistician and president of the think tank Copenhagen Consensus Center. He is former director of the Danish government's Environmental Assessment Institute (EAI) in Copenhagen. He became internationally known for his best-selling and controversial book The Skeptical Environmentalist (2001).

Lomborg was a statistician associated with Aarhus University. His first book The Skeptical Environmentalist, which argued many environmental issues are overstated, attracted criticism from the scientific community and brought Lomborg popular media attention. In 2002, Lomborg and the Environmental Assessment Institute founded the Copenhagen Consensus. In 2004, he was listed as one of Time's 100 most influential people.

In his subsequent book, Cool It (2007), and its film adaptation, Lomborg outlined his views on global warming. These include his view that negative impacts are overstated and his opposition to climate change mitigation. In 2009, Business Insider cited Lomborg as one of "The 10 Most-Respected Global Warming Skeptics".

Lomborg's views and work have attracted scrutiny in the scientific community. The majority of scientists reacted negatively to The Skeptical Environmentalist and he was formally accused of scientific misconduct over the book; the Danish Committees on Scientific Dishonesty concluded in an evaluation of the book that "one couldn't prove that Lomborg had deliberately been scientifically dishonest, although he had broken the rules of scientific practice in that he interpreted results beyond the conclusions of the authors he cited." His positions on climate change have been challenged by experts and characterised as cherry picking.