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 (Erie County, New York)
• 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