Lieutenant William Portwood Erwin (18 October 1895 – 19 August 1927) was an American World War I flying ace credited with eight aerial victories.

As a Salmson 2A2 pilot, he scored his victories between 15 September and 22 October 1918; half of them were with gunner Arthur Easterbrook.

[6] Erwin and Eichwaldt would fly the Dallas Spirit,[7] a custom aircraft built by the Swallow Airplane Company on credit for the attempt.

Erwin and Eichwaldt's air race attempt was aborted shortly after takeoff due to mechanical problems.

After returning to the airport to have the problems fixed, Erwin got word that two competitor's planes had gone missing during the attempt.