List of highways numbered 400

Australia

• Murray Valley Highway

  Canada

• Ontario Highway 400

  Croatia

• D400 road

  Cuba

• Vía Monumental

  Ireland

• R400 road

  Japan

• Japan National Route 400

  Korea, South

• Capital Region Second Ring Expressway

  South Africa

• R400 road in the Eastern Cape

  Spain

• N-400 road

  Turkey

• , a west–east state road in Turkey running from Datça, Muğla Province to Esendere at the Iranian border.

  United Kingdom

• A400 road in London
• B400 road

  United States

• U.S. Route 400
• Arkansas Highway 400
• Florida State Road 400
• Georgia State Route 400
• Kentucky Route 400
• Louisiana Highway 400
• Maryland Route 400, a former state highway
• Nevada State Route 400
• New York:
• * New York State Route 400
• * County Route 400
• North Carolina Highway 400
• Pennsylvania Route 400
• Puerto Rico Highway 400
• South Carolina Highway 400
• Tennessee State Route 400
• Texas:
• * Texas State Highway Spur 400
• * Farm to Market Road 400
• Utah:
• * Road 400
• Virginia State Route 400
• * Virginia State Route 400