The following highways are numbered 403:

Canada

• Manitoba Provincial Road 403
• Newfoundland and Labrador Route 403
• Highway 403 (Ontario)

Costa Rica

• National Route 403

Croatia

• D403 road

Hungary

• Main road 403 (Hungary)

Japan

• Japan National Route 403

Thailand

• Thailand Route 403

United States

• Georgia State Route 403 (unsigned designation for Interstate 85)
• Indiana State Road 403 (former)
• New York:
  • New York State Route 403
  • County Route 403 (Albany County, New York)
  • County Route 403 (Erie County, New York)
• North Carolina Highway 403
• Pennsylvania Route 403
• Puerto Rico Highway 403
• Rhode Island Route 403
• South Carolina Highway 403
• Virginia State Route 403
• Washington State Route 403