Saint Elmo or St. Elmo may refer to:

• Erasmus of Formia or Saint Elmo (died 303), patron saint of sailors
• Peter González or Saint Elmo (1190–1246), Castilian Dominican friar and priest
• St. Elmo Brady (1884–1966), first African American to obtain a Ph.D. in chemistry in the United States

• Fort Saint Elmo, a fortress in Valletta
• St. Elmo Bridge, a bridge located close to the above fort

• St. Elmo, Alabama
• Saint Elmo, Colorado
• St. Elmo (Columbus, Georgia), a historic residence
• St. Elmo, Illinois
• St. Elmo, Louisiana, a community in Ascension Parish, Louisiana
• St. Elmo, Michigan, a community in Midland County
• St. Elmo Historic District (Chattanooga, Tennessee)
• St. Elmo Steak House, a restaurant in Indianapolis, Indiana, U.S.

• St. Elmo, a nickname for the fraternity of Delta Phi
• St. Elmo Society, a senior secret society at Yale University
• St. Elmo Hall, a building formerly owned by the St. Elmo Society at Yale University
• St. Elmo Hall, a nickname for the fraternity of Delta Phi

• St. Elmo (novel), an 1866 novel by Augusta Jane Evans, which spawned numerous silent film adaptations:
  • St. Elmo (1910 Thanhouser film)
  • St. Elmo (1910 Vitagraph film)
  • St. Elmo (1914 film)
  • St. Elmo (1923 American film)
  • St. Elmo (1923 British film)
• Saint Elmo (comics), a member of the Marvel Comics team Alpha Flight
• Saint Elmo – Hikari no Raihousha, an anime television special

• Ida Saint-Elme, pen name of Maria Verfelt (1776–1845), Dutch writer and actress
• Fort Saint-Elme (France), Collioure
• Sant'Elmo, a hill and a fortress in Naples, Italy
• Elmo (disambiguation)
• San Telmo (disambiguation)
• Santelmo, a creature of Philippine mythology
• St. Elmo's Fire (disambiguation)