D20, D-20 or d20 may refer to:

Arts, entertainment, and media

  • d20, a 20-sided die commonly used in role-playing games
  • d20 System, a role-playing game system published by Wizards of the Coast
  • Arriflex D-20, a film-style digital high definition movie camera
  • D-20, a version of the Roland D-50 synthesizer
  • Dimension 20, a tabletop role-playing game show made by CollegeHumor/Dropout
  • Queen's Gambit Accepted, Encyclopaedia of Chess Openings code

Military

  • 152 mm gun-howitzer D-20, a Soviet artillery piece
  • , a destroyer that served with the Argentine Navy between 1961 and 1982
  • , a destroyer escort that served with the Brazilian Navy between 1944 and 1975
  • , a destroyer that served with the Royal Hellenic Navy between 1951 and 1972
  • , a Royal Navy guided missile destroyer launched in 1964 and decommissioned in 1987

Science

  • D20, a diffractometer located at Institut Laue–Langevin used in neutron research
  • Heavy water, or deuterium oxide (D<sub>2</sub>O or <sup>2</sup>H<sub>2</sub>O)

Vehicles and transport

  • D20 road (Croatia), a state road
  • Aero Synergie Jodel D20, a French ultralight
  • Chevrolet D-20, a pick-up truck made in Brazil and Argentina
  • H Street Line, a Washington DC Metrobus route, designated D20
  • LNER D20, a class of British steam locomotives
  • Senova D20, a subcompact car made by SAIC in China
  • Soloviev D-20, a Soviet turbofan engine

Other

  • Dublin 20, a Dublin, Ireland postal district
  • 2020 Democratic National Convention, American political convention, branded as "D20"