Keyes DeWitt Metcalf was an American librarian. He has been identified as one of the 100 most important leaders in librarianship by the journal American Libraries. In a career spanning over 75 years, he worked in various roles at the New York Public Library and served as the director of the Harvard University library system. He was known for his expertise in planning and designing research libraries.

Harvard Library is the network of Harvard University's libraries and services. It is the oldest library system in the United States and both the largest academic library and largest private library in the world. Its collection holds over 20 million volumes, 400 million manuscripts, 10 million photographs, and one million maps.