Ruis can mean:

  • Ruis (letter), a letter of the Ogham alphabet
  • Ruis, Switzerland, a kreis in Switzerland
  • the municipality of Rueun in Switzerland, formerly known as Ruis
  • Rye, which translates to "ruis" in the Finnish language
  • RUIS acronym of Revolutionary Union for Internationalist Solidarity, an anarchist militia in the Syrian Civil War.