Erna may refer to:

• Erna (given name), a list of people with the name
• Jeff Erna, American drummer
• Sully Erna (born 1968), American musician and member of Godsmack
• pen name of Anna van Gogh-Kaulbach (1869-1960), Dutch writer
• Érna, or Iverni, a people of medieval Ireland

• Erna (mythology), a figure in Norse mythology
• Erna (moth), genus of moths in the family Erebidae
• Little Erna, the butt of Little Erna jokes popular in Hamburg
• Erna (planet), a fictional world in C. S. Friedman's Coldfire Trilogy
• Erna long-range reconnaissance group, a Finnish Army unit of Estonian volunteers which operated behind Red Army lines in World War II
• Erna Raid, a former military exercise held annually in Estonia
• Erna, Texas, United States, an unincorporated community
• 406 Erna, a main belt asteroid
• Enhancer RNAs
• SS Erna, a German coaster in service 1922-46

• Urna (disambiguation)