Highway 138 may refer to:
Canada
- 25px Ontario Highway 138
- 25px Prince Edward Island Route 138
- 25px Quebec Route 138
Costa Rica
- 25px National Route 138
India
- 25px National Highway 138 (India)
Japan
- 25px Japan National Route 138
- 25px Fukuoka Prefectural Route 138
- 25px Nara Prefectural Route 138
Malaysia
- 25px Malaysia Federal Route 138
United Kingdom
- road
- B138 road
United States
- 25px U.S. Route 138
- 25px Alabama State Route 138
- 25px County Route 138 (Lee County, Alabama)
- 25px Arkansas Highway 138
- 25px California State Route 138
- 25px Connecticut Route 138
- 25px Florida State Road 138 (former)
- 25px County Road 138 (Columbia County, Florida)
- 25px County Road 138 (Gilchrist County, Florida)
- 25px County Road 138A (Lafayette County, Florida)
- 25px County Road 138 (Pinellas County, Florida)
- 25px Georgia State Route 138
- 25px Hawaii Route 138
- 25px Illinois Route 138
- 25px K-138 (Kansas highway)
- 25px Kentucky Route 138
- 25px Louisiana Highway 138
- 25px Maine State Route 138
- 25px Maryland Route 138
- 25px Massachusetts Route 138
- 25px M-138 (Michigan highway)
- 25px Missouri Route 138
- 25px New Jersey Route 138
- 25px New Mexico State Road 138
- 25px New York State Route 138
- 25px County Route 138 (Herkimer County, New York)
- 25px County Route 138 (Niagara County, New York)
- 25px County Route 138 (Onondaga County, New York)
- 25px North Carolina Highway 138
- 25px Ohio State Route 138
- 25px Oregon Route 138
- 25px Pennsylvania Route 138
- 25px Rhode Island Route 138
- 25px Rhode Island Route 138A
- 25px Tennessee State Route 138
- 25px Texas State Highway 138
- 25px Texas State Highway Spur 138
- 25px Farm to Market Road 138
- 25px Utah State Route 138
- 25px Utah State Route 138 (1933-1953) (former)
- 25px Virginia State Route 138
- 25px Virginia State Route 138 (1930-1933) (former)
- 25px Wisconsin Highway 138
- 25px Wyoming Highway 138 (former)
;Territories:
- 25px Puerto Rico Highway 138