Alexius Frederick, Prince of Bentheim and Steinfurt (20 January 1781 – 3 November 1866) was a German nobleman.
His father was Prince Louis William Geldricus Ernest of Bentheim and Steinfurt; his mother was Juliane Wilhelmine of Schleswig-Holstein-Sonderburg-Glücksburg He studied in Marburg under Johann Stephan Pütter.
In 1821, the Bentheim-Tecklenburg-Rheda line of the family sued him, claiming to have better rights to the counties of Bentheim and Steinfurt.
Incidentally, the County of Bentheim had been pledged to Hanover long before his reign.
Alexius was a member of the provincial parliament of the Prussian province of Westphalia.