The 100: A Ranking of the Most Influential Persons in History is a 1978 book by Michael H. Hart. It is a ranking of the 100 people who, in his opinion, most influenced human history. Since publication the book has been hotly debated and its concept widely copied. It is important to note that Dr. Hart did not rank the greatest people. His criterion was influence.

The book was reprinted in 1992 with several notable revisions made to the original list of 100 people and their associated rankings. Chief among these revisions was the demotion of figures associated with Communism, such as Vladimir Lenin and Mao Zedong, and the introduction of Mikhail Gorbachev. Hart took sides in the Shakespearean authorship issue and substituted Edward de Vere, 17th Earl of Oxford for William Shakespeare. Hart also substituted Niels Bohr and Henri Becquerel with Ernest Rutherford, thus correcting an error in the first edition. Henry Ford was also promoted from the "Honorary Mentions" list, replacing Pablo Picasso. Finally, some of the rankings were re-ordered, although no one listed in the top ten changed position.