Class 31 may refer to:

  • British Rail Class 31
  • EAR 31 class
  • GER Class N31
  • HSH Class 31
  • L&YR Class 31
  • NBR Class M 4-4-0, later LNER Class D31
  • No.31-class patrol boat
  • Seibu Class E31
  • South African Class 31-000