ER2, ER-2, etc. may refer to:

  • Elizabeth II, Queen of the United Kingdom and other realms, from the Latin ER II (Elizabeth Regina II) inscribed on coins, etc.
  • "ER2" (Kanjani Eight song), a single by Japanese boy band Kanjani Eight
  • ER2 electric trainset, an electric passenger railcar built in Latvia and Russia from 1962 to 1984
  • NASA ER-2, "Earth Resources 2", an American very high-altitude civilian atmospheric research fixed-wing aircraft based on the Lockheed U-2 reconnaissance aircraft