Leidyosuchus sternbergii was named by Gilmore (1910). Its type specimen is U.S.N.M. No. 6533, a partial skeleton (mostly complete skull, left ramus, partial right ramus, eight vertebrae, both humeri, right fibula, and other postcrania), and it is a 3D body fossil. Its type locality is West of McKeow's Ranch, which is in a Maastrichtian terrestrial horizon in the Lance Formation of Wyoming.

It was synonymized subjectively with Leidyosuchus canadensis by Lucas and Sullivan (1986); it was misspelled as Leidyosuchus sternbergi by Bryant (1989); it was recombined as Borealosuchus sternbergii by Brochu (1997), Brochu (2000), Wu et al. (2001), Puértolas et al. (2011), Bronzati et al. (2012), Lessner et al. (2025).