List of highways numbered 321

Canada

• Nova Scotia Route 321
• Saskatchewan Highway 321

  China

• China National Highway 321

  Costa Rica

• National Route 321

  Japan

• Japan National Route 321

  United States

• U.S. Highway 321
• Arkansas Highway 321
• * Arkansas Highway 321 Spur
• Georgia State Route 321
• Kentucky Route 321
• Louisiana Highway 321
• Mississippi Highway 321
• Nevada State Route 321
• New Mexico State Road 321
• New York:
• * New York State Route 321
• * County Route 321
• North Carolina Highway 321
• Ohio State Route 321
• Pennsylvania Route 321
• Puerto Rico Highway 321
• Tennessee State Route 321
• Texas:
• * Texas State Highway 321
• * Texas State Highway Loop 321
• * Farm to Market Road 321
• Virginia State Route 321
• * Virginia State Route 321
• Wyoming Highway 321