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)