Theodore Frelinghuysen Singiser (March 15, 1845 – January 23, 1907) was a Delegate from Idaho Territory.

Born in Churchtown in Cumberland County, Pennsylvania, Singiser attended the common schools.

He learned the art of printing, and then enlisted in the Union Army as a private in Company E, Sixth Regiment, Pennsylvania Reserves, on June 6, 1861.

He served as assistant assessor of internal revenue in 1866 and 1867, and engaged in mercantile and editorial pursuits.

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