1. Australia

2. Canada

3. Croatia

4. Ireland

5. Japan

6. Korea, South

7. South Africa

8. Spain

9. Turkey

10. United Kingdom

11. United States

The following highways are numbered 400:

Australia

• {{AUshield|VIC|B400}} Murray Valley Highway

Canada

• Ontario Highway 400

Croatia

• D400 road

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

• {{TUR-D|400}}, 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 (Chancery Lane)

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 (official designation for Pennsylvania Route 380)
• South Carolina Highway 400
• Tennessee State Route 400
• Texas:
  • Texas State Highway Spur 400
  • Farm to Market Road 400
• Utah:
  • Road 400 (Cottonwood Canyon Road)
• Virginia State Route 400
  • Virginia State Route 400 (former)

• Arellano University – Plaridel Campus
• Arella x
• Arellia (gens)
• Arellius
• Arema
• Arema F.C. U-21
• Arema Indonesia
• Arema Indonesia Football Club
• Arema Malang
• Aremania
• Aremberg, Prince Charles d'
• Are Me
• A Remedy to Cure All Ills
• Arem language
• AREMOS
• Are (moth)
• Are Municipality
• Arena (1953 film)
• Arena 2
• Arena (2009 film)
• Arena (2011 film)
• Arena (active protection system)
• Arena Active Protection System
• Arena (album)
• Arena allocation