Efraim Karsh (Hebrew: אפרים קארש; born 6 September 1953) is an Israeli and British historian who is the founding director and emeritus professor of Middle East and Mediterranean Studies at King's College London. Since 2013, he has served as professor of political studies at Bar-Ilan University (where he also directs the Begin-Sadat Center for Strategic Studies). He is also a principal research fellow and former director of the Middle East Forum, a Philadelphia-based think tank. He is a vocal critic of the New Historians, a group of Israeli scholars who have questioned the traditional Israeli narrative of the Arab–Israeli conflict.

Born and raised in Israel to Jewish immigrants to the Palestine Mandate, Karsh graduated in Arabic and Modern Middle East History from the Hebrew University in Jerusalem, and obtained an MA and PhD in International Relations from Tel Aviv University. After acquiring his first academic degree in modern Middle Eastern history, he was a research analyst for the Israel Defense Forces (IDF), where he attained the rank of major.^{[citation needed]}

Karsh has held various academic posts at Harvard and Columbia universities, the Sorbonne, the London School of Economics, Helsinki University, the International Institute for Strategic Studies in London, the Kennan Institute for Advanced Russian Studies in Washington D.C., and the Jaffee Center for Strategic Studies at Tel Aviv University. In 1989 he joined King's College London, where he established the Middle East and Mediterranean Studies Program, directing it for 16 years. He has published extensively on Middle Eastern affairs, Soviet foreign policy, and European neutrality, and is a founding editor of the scholarly journal Israel Affairs, and editor of the Middle East Quarterly. He is a regular media commentator, has appeared on all the main radio and television networks in the United Kingdom and the United States, and has contributed articles to leading newspapers, including The New York Times, The Los Angeles Times,The Wall Street Journal, The Times (London) and The Daily Telegraph.

In his 2010 book Palestine Betrayed, followed by a 2011 editorial in Haaretz, Karsh articulated his belief that the 1948 Palestinian expulsion and flight was "exclusively of their own making". Karsh writes that many Palestinians fled their homes as the result of pressure from local Arab leaders "and/or the Arab Liberation Army that had entered Palestine prior to the end of the Mandate (Mandatory Palestine), whether out of military considerations or in order to prevent them from becoming citizens of the prospective Jewish state." He stated that there is an "overwhelming and incontrovertible body of evidence" to support his position including "intelligence briefs, captured Arab documents, press reports, personal testimonies and memoirs..." Karsh states that "the deliberate depopulation of Arab villages and their transformation into military strongholds" began in December 1947.

Karsh rejects the Palestinian demands for a right of the return, citing a need for Israel to maintain its Jewish character. "However, even if the more restrictive Israeli figures were to be accepted, it is certainly true, just as Amos Oz darkly predicts, that the influx of these refugees into the Jewish State would irrevocably transform its demographic composition. At the moment, Jews constitute about 79 percent of Israel's six-million-plus population, a figure that would rapidly dwindle to under 60 percent. Given the Palestinians' far higher birth rate, the implementation of a 'right of return', even by the most conservative estimates, would be tantamount to Israel's transformation into an 'ordinary' Arab state."

Karsh's Empires of the Sand: The Struggle for Mastery in the Middle East, 1789–1922 was published in 1999, co-written by his wife Inari Rautsi-Karsh.

Daniel Pipes called it a "tour de force that offers a profoundly new understanding of a key issue in modern Middle Eastern history:" and said that " Drawing on a wide range of original sources, and writing in a clearly organized fashion and in fast-paced prose, the Karshes make a very compelling case for their revisionist position, establishing it point by point and in elegant detail".^{[unreliable source]}

Anthony B. Toth wrote in a review: "This is a polemical book whose authors have extended the intemperate and unbalanced rhetoric customarily employed by dogmatic partisans of the Arab Israeli conflict to the normally sedate and measured arena of nineteenth - and early twentieth-century Ottoman history. The book relies mainly on Western published sources and official documents of the British government. But their use of even these sources is limited, since they actually ignore most of nineteenth-century history. Instead, the authors emphasize those episodes they feel support their interpretations".