Albertosaurus is a member of the theropod family Tyrannosauridae, in the subfamily Albertosaurinae.
Its closest relative is the slightly older Gorgosaurus libratus (sometimes called Albertosaurus libratus; see below).
These two species are the only described albertosaurines; other undescribed species may exist.
Thomas Holtz found Appalachiosaurus to be an albertosaurine in 2004, but his more recent unpublished work locates it just outside Tyrannosauridae, in agreement with other authors.

The other major subfamily of tyrannosaurids is the Tyrannosaurinae, which includes Daspletosaurus, Tarbosaurus and Tyrannosaurus.
Compared with these robust tyrannosaurines, albertosaurines had slender builds, with proportionately smaller skulls and longer bones of the lower leg (tibia) and feet (metatarsals and phalanges).

Below is the cladogram of the Tyrannosauridae based on the phylogenetic analysis conducted by Loewen et al.
in 2013.
Albertosaurus is a member of the theropod family Tyrannosauridae, in the subfamily Albertosaurinae. Its closest relative is the slightly older Gorgosaurus libratus (sometimes called Albertosaurus libratus; see below). These two species are the only described albertosaurines; other undescribed species may exist. Thomas Holtz found Appalachiosaurus to be an albertosaurine in 2004, but his more recent unpublished work locates it just outside Tyrannosauridae, in agreement with other authors.
The other major subfamily of tyrannosaurids is the Tyrannosaurinae, which includes Daspletosaurus, Tarbosaurus and Tyrannosaurus. Compared with these robust tyrannosaurines, albertosaurines had slender builds, with proportionately smaller skulls and longer bones of the lower leg (tibia) and feet (metatarsals and phalanges).
Below is the cladogram of the Tyrannosauridae based on the phylogenetic analysis conducted by Loewen et al. in 2013.
Albertosaurus