Wyoming Highway 138 (WYO 138) was a 8.14-mile-long (13.10 km) east-west (southwest-northeast) Wyoming State Road in central Fremont County.

WYO 138 proceeded in a northeasterly direction, and traveled through the community (CDP) of Arapahoe.

Just northeast of Arapahoe, WYO 138 reached Wyoming Highway 137 in the unincorporated community of St. Stephens where it ended.

[2][3] Together with WYO 137, Highway 138 provided an alternate to WYO 789 by staying closer to the Popo Agie River.

[3] A resolution to relinquish the highway to the Bureau of Indian Affairs was approved by the Transportation Commission of Wyoming at a meeting on December 9, 2010.