Justice Duncan or Judge Duncan, may refer to:
Laurence Ilsley Duncan (1906–1982), associate justice of the New Hampshire Supreme Court Rebecca Duncan (born 1971), associate justice of the Oregon Supreme Court Robert Morton Duncan (1927–2012), associate justice of the Ohio Supreme Court Warren W. Duncan (1857–1938), associate justice of the Illinois Supreme Court
See also Benjamin Faneuil Dunkin, chief justice of the South Carolina Supreme Court Judge Duncan (disambiguation)