This is a list of roads designated A21. Roads are sorted in the countries' alphabetical order.

• City Ring Route in Adelaide, South Australia
• A21 (Toowoomba, Queensland)
• A21 motorway (Austria), a road connecting Altlengbach and the A1 to Vösendorf and the A2
• A21 road (England), a road connecting London with Hastings on the south coast
• A21 motorway (France), a road connecting Aix-Noulette and Douai
• A 21 motorway (Germany), a road connecting the road interchange with the A 1 at Bargteheide with Wankendorf
• A21 motorway (Italy), a road connecting Turin and Brescia
• A-21 motorway (Spain), a road connecting Jaca, Aragon and Pamplona, Navarre
• A 21 road (Sri Lanka), a road connecting Kegalle and Karawanella
• A21 road (United States of America) may refer to:
  • A21 road (California), a road

• List of highways numbered 21
• List of 21A roads

This article includes a list of roads, streets, highways, or other routes that are associated with the same title.
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