John Ivan Simon (né Simmon; May 12, 1925 − November 24, 2019) was an American author and literary, theater, and film critic. After spending his early years in Belgrade, he moved to the United States, serving in the United States Army Air Forces during World War II and studying at Harvard University. Beginning in the 1950s, he wrote arts criticism for a variety of publications, including a 36-year tenure as theatre critic for New York magazine, and latterly as a blogger.