Widnoon is an unincorporated community located near the center of Madison Township, Armstrong County, Pennsylvania, United States.

Widnoon had its own post office from March 22, 1880, to February 3, 2005.

[3][4] Duncanville, later called Widnoon, appears in the 1876 Atlas of Armstrong County, Pennsylvania.

[7] The United Brethren and the Presbyterians had organized churches here and houses of worship in 1878 which were no longer in use by 1913.

314, covered by warrant 2868, called "Elliott Grove," which adjoined the original line between Toby and Red Bank townships on the east.