Felsenthal is a town in Union County, Arkansas, United States.

It lays adjacent to the Ouachita River in the southeastern corner of Union County.

As of the census[5] of 2000, there were 152 people, 70 households, and 44 families residing in the town.

30.0% of all households were made up of individuals, and 10.0% had someone living alone who was 65 years of age or older.

About 2.4% of families and 11.5% of the population were below the poverty line, including 16.0% of those under the age of 18 and 21.2% of those 65 or over.