James Hadley Billington (June 1, 1929 – November 20, 2018) was an American academic and author who taught history at Harvard and Princeton before serving for 42 years as CEO of four federal cultural institutions. He served as the 13th Librarian of Congress after being nominated by President Ronald Reagan in 1987, and his appointment was approved unanimously by the U.S. Senate. He retired as Librarian on September 30, 2015.

Born in Bryn Mawr, Pennsylvania, Billington was educated in Philadelphia-area public schools. He was class valedictorian at both Lower Merion High School and Princeton University, where he graduated with highest honors and an A.B. in history in 1950 after completing a senior thesis titled "Nicholas Berdyaev." Three years later, he earned his doctorate in Russian history from Balliol College of the University of Oxford, where he was a Rhodes Scholar and student of the philosopher Isaiah Berlin.

Following service with the U.S. Army and the Office of National Estimates, he taught history at Harvard University from 1957 to 1962 and subsequently at Princeton University, where he was a professor of history from 1964 to 1974.

From 1973 to 1987, Billington was director of the Woodrow Wilson International Center for Scholars, the nation's official memorial in Washington, D.C., to America's 28th president. As director, he founded the Kennan Institute for Advanced Russian Studies at the center, and seven other new programs, as well as the Wilson Quarterly.

Billington was married to the former Marjorie Anne Brennan. They had four children: Susan Billington Harper, Anne Billington Fischer, the Rev. James Hadley Billington Jr., and Thomas Keator Billington, as well as 12 grandchildren. Billington and his daughter Susan were the first father and daughter to both be awarded Rhodes Scholarships and to use them to earn Doctorates of Philosophy at Oxford University.

Billington was sworn in as the Librarian of Congress on September 14, 1987. He was the 13th person to hold the position since the Library of Congress was established in 1800. He was nominated by President Ronald Reagan and his appointment was unanimously confirmed by the Senate.

During his tenure at the Library of Congress, Billington doubled the size of the Library's traditional analog collections, from 85.5 million items in 1987 to more than 160 million items in 2014. He led the acquisition of Lafayette's previously inaccessible papers in 1996 from Château de la Grange-Bléneau in France. Billington has since been the only non-Frenchman on the board of the foundation governing the castle. He also acquired the only copy of the 1507 Waldseemüller world map ("America's birth certificate") in 2003 for permanent display in the Library's Thomas Jefferson Building.

Billington pioneered the reconstruction, using privately raised funds, of Thomas Jefferson's original library, which was placed on permanent display in the Jefferson building in 2008. He enlarged and technologically enhanced public spaces of the Jefferson Building into a national exhibition venue, and hosted over 100 exhibitions, most featuring materials not previously displayed publicly in the United States. These included exhibits on the Vatican Library and the Bibliothèque Nationale de France, several on the Civil War and Lincoln, on African-American culture, on Religion and the founding of the American Republic, the Early Americas (the Kislak Collection is now on permanent display), and the global celebration commemorating the 800th anniversary of Magna Carta, and on early American printing featuring the Rubenstein Bay Psalm Book. Billington also advocated successfully for an underground connection between the U.S. Capitol Visitors Center and the Library in 2008 to increase congressional usage and public tours of the Library's Thomas Jefferson Building.