Highway 138 may refer to:

Canada

• Ontario Highway 138
• Prince Edward Island Route 138
• Quebec Route 138

Costa Rica

• National Route 138

India

• National Highway 138 (India)

Japan

• Japan National Route 138
• Fukuoka Prefectural Route 138
• Nara Prefectural Route 138

Malaysia

• Malaysia Federal Route 138

United States

• U.S. Route 138
• Alabama State Route 138
• Arkansas Highway 138
• California State Route 138
• Connecticut Route 138
• Florida State Road 138 (former)
  • County Road 138 (Columbia County, Florida)
  • County Road 138 (Gilchrist County, Florida)
  • County Road 138A (Lafayette County, Florida)
  • County Road 138 (Pinellas County, Florida)
• Georgia State Route 138
• Hawaii Route 138
• Illinois Route 138
• K-138 (Kansas highway)
• Kentucky Route 138
• Louisiana Highway 138
• Maine State Route 138
• Maryland Route 138
• Massachusetts Route 138
• M-138 (Michigan highway)
• Missouri Route 138
• New Jersey Route 138
• New Mexico State Road 138
• New York State Route 138
  • County Route 138 (Herkimer County, New York)
  • County Route 138 (Niagara County, New York)
  • County Route 138 (Onondaga County, New York)
• North Carolina Highway 138
• Ohio State Route 138
• Oregon Route 138
• Pennsylvania Route 138
• Rhode Island Route 138
  • Rhode Island Route 138A
• Tennessee State Route 138
• Texas State Highway 138
  • Texas State Highway Spur 138
  • Farm to Market Road 138
• Utah State Route 138
  • Utah State Route 138 (1933-1953) (former)
• Virginia State Route 138
  • Virginia State Route 138 (1930-1933) (former)
• Wisconsin Highway 138
• Wyoming Highway 138 (former)

Territories

• Puerto Rico Highway 138