Marjabelle Young Stewart (16 May 1924 – 3 March, 2007) was an American writer and expert on etiquette.

Marjabelle Young Stewart was born in Council Bluffs, Iowa to a great-grandson of poet William Cullen Bryant. She lived in an orphanage after her parents divorced. She married scientist Jack Davison Young and moved to Washington, D.C. in 1941. She became a model and came into contact with Washington society as a result. She moved to Kewanee, Illinois in 1962 after marriage to attorney William E. Stewart. She went on to teach etiquette and manners to American Presidents such as Lyndon B. Johnson, Richard Nixon, and Ronald Reagan.

Stewart died of pneumonia at a Kewanee nursing home, at the age of 82 (http://news.yahoo.com/s/ap/20070304/ap_on_re_us/obit_stewart_1).