William Allen Trimble (April 4, 1786 – December 13, 1821) was a Democratic-Republican politician from Ohio.

He briefly practiced law in Highland County, Ohio, from 1811 to 1812.

[1] In the subsequent years he served in a variety of capacities, mostly with the Ohio militia and the U.S. Army in campaigns against the Pottawatomie Indians.

He was promoted to lieutenant colonel of the First United States Infantry in 1814.

[2] He was transferred to the Eighth United States Infantry in 1815 and served there until his resignation in 1819, following his election to the U.S. Senate for the term beginning in 1819.