The following highways are numbered 300:

Australia

• Midland Highway (Victoria)
• Melba Highway (Victoria)

Canada

• Manitoba Provincial Road 300

Japan

• Japan National Route 300

Korea, South

• Daejeon Southern Ring Expressway

Turkey

• D.300, a west-east state road in Turkey running from Çeşme, İzmir Province to Kapıköy at the Iranian border.

United States

• Arkansas Highway 300
• Colorado State Highway 300
• Delaware Route 300
• Florida State Road 300
• Georgia:
  • Georgia State Route 300
    • Georgia State Route 300 Connector
    • Georgia State Route 300 (former)
• Iowa Highway 300 (former)
• Kentucky Route 300
• Louisiana Highway 300
• Maryland Route 300
• Minnesota State Highway 300
• Montana Secondary Highway 300
• New Jersey Route 300 (former)
• New Mexico State Road 300
• New York State Route 300
• Ohio State Route 300
• Pennsylvania Route 300 (official designation for Pennsylvania Route 283)
• Puerto Rico Highway 300
• South Carolina Highway 300
• Tennessee State Route 300 (unsigned)
• Texas:
  • Texas State Highway 300
  • Texas State Highway Spur 300
  • Farm to Market Road 300
• Utah State Route 300 (former)
• Virginia State Route 300
• Washington State Route 300