William Cogswell (August 23, 1838 – May 22, 1895) was a U.S. Representative from Massachusetts and a colonel in the Union Army during the American Civil War who was appointed to the grade of brevet brigadier general, U.S.

Cogswell's father was a well-respected surgeon and one of the founders of the Massachusetts Republican Party.

Cogswell was a private in the Second Corps of Cadets, a militia organization of the Commonwealth of Massachusetts.

On April 19, 1861, word reached Salem that the Sixth Massachusetts had been attacked in Baltimore while on its way to defend Washington, D.C. Cogswell turned his office into a recruiting station and in 24 hours raised a full company, the first company in the country recruited for the war.

Cogswell remarried to Eva M. Davis on December 12, 1881 and they remained married until his death, having no children.

This article incorporates public domain material from the Biographical Directory of the United States Congress