Western Sahara is around the same size as Wyoming.

Wyoming is approximately 251,489 sq km, while Western Sahara is approximately 266,000 sq km, making Western Sahara 6% larger than Wyoming. Meanwhile, the population of Wyoming is ~563,626 people (88,645 more people live in Western Sahara).
Tip: This to-scale comparison of Wyoming vs. Western Sahara uses the Mercator projection, which distorts the size of regions near the poles.