Established in 1636, Harvard University is a private Ivy League research university and the oldest institution of higher learning in the United States. Its endowment is valued at $41.9 billion, making it the largest of any academic institution in the world. It also has the world’s largest academic library system, comprising 79 individual libraries holding about 20.4 million items. Its alumni include eight U.S. presidents, 188 living billionaires, 369 Rhodes Scholars, 252 Marshall Scholars, and 11 Mitchell Scholars. Furthermore, 161 Nobel laureates, 18 Fields Medal winners, and 14 Turing Award laureates have been affiliated with the university as students, faculty, or researchers. Harvard University is ranked as the best university in the world by the Academic Ranking of World Universities and U.S. News & World Report Best Global University Ranking, and third in the world by QS World University Rankings and Times Higher Education World University Rankings.