The following highways are numbered 303:

Canada

• New Brunswick Route 303
• Nova Scotia Route 303
• Prince Edward Island Route 303
• Quebec Route 303
• Saskatchewan Highway 303

China

• China National Highway 303

Costa Rica

• National Route 303

India

• National Highway 303 (India)

Japan

• Japan National Route 303

Philippines

• N303 highway (Philippines)

United Kingdom

• A303 road (Basingstoke-Honiton)

United States

• Arizona State Route 303
• Arkansas Highway 303
• Georgia State Route 303
• Indiana State Road 303
• Kentucky Route 303
• Louisiana Highway 303
• Maryland Route 303
• Minnesota State Highway 303 (former)
• New Jersey Route 303 (never built)
• New York:
  • New York State Route 303
  • County Route 303 (Albany County, New York)
  • County Route 303 (Erie County, New York)
  • County Route 303 (Westchester County, New York)
• North Carolina Highway 303 (former)
• Ohio State Route 303
• Pennsylvania Route 303 (former)
• South Carolina Highway 303
• Tennessee State Route 303
• Texas:
  • Texas State Highway 303 (former)
  • Texas State Highway Spur 303
  • Farm to Market Road 303
  • Urban Road 303 (signed as Farm to Market Road 303)
• Utah State Route 303
• Virginia State Route 303
• Washington State Route 303

Other areas:

• Puerto Rico Highway 303
• U.S. Virgin Islands Highway 303