K
- Thomas Kean, former New Jersey governor; former chairman of the 9/11 Commission; former president of Drew University
- Robert Winthrop Kean, U.S. representative from New Jersey from 1938–1959
- John Marshall Kernochan, IPR pioneer and founder of Columbia Law School's Kernochan Center for Law, Media, and the Arts
- Suzanne P. King, US Olympic cross country skier, 1994 and 1998 Olympic games
- William A. Knowlton, four star general, former superintendent of West Point
Read more about this topic: List Of St. Mark's School (Massachusetts) Alumni