Gorgosaurus is classified in the theropod subfamily Albertosaurinae within the family Tyrannosauridae.
It is most closely related to the slightly younger Albertosaurus.
These are the only two definite albertosaurine genera that have been described, although other undescribed species may exist.
Appalachiosaurus was described as a basal tyrannosauroid just outside Tyrannosauridae, although American paleontologist Thomas Holtz published a phylogenetic analysis in 2004 which indicated it was an albertosaurine.
More recent, unpublished work by Holtz agrees with the original assessment.
All other tyrannosaurid genera, including Daspletosaurus, Tarbosaurus and Tyrannosaurus, are classified in the subfamily Tyrannosaurinae.
Compared to the tyrannosaurines, albertosaurines had slender builds, with proportionately smaller, lower skulls and longer bones of the lower leg (tibia) and feet (metatarsals and phalanges).

The close similarities between Gorgosaurus libratus and Albertosaurus sarcophagus have led many experts to combine them into one genus over the years.
Albertosaurus was named first, so by convention it is given priority over the name Gorgosaurus, which is sometimes considered its junior synonym.
William Diller Matthew and Barnum Brown doubted the distinction of the two genera as early as 1922.
Gorgosaurus libratus was formally reassigned to Albertosaurus (as Albertosaurus libratus) by Dale Russell in 1970, and many subsequent authors followed his lead.
Combining the two greatly expands the geographical and chronological range of the genus Albertosaurus.
Other experts maintain the two genera as separate.
Canadian paleontologist Phil Currie claims there are as many anatomical differences between Albertosaurus and Gorgosaurus as there are between Daspletosaurus and Tyrannosaurus, which are almost always kept separate.
He also notes that undescribed tyrannosaurids discovered in Alaska, New Mexico and elsewhere in North America may help clarify the situation.
Gregory S. Paul has suggested that Gorgosaurus libratus is ancestral to Albertosaurus sarcophagus.

Below is the cladogram of Tyrannosauridae based on the phylogenetic analysis conducted by Loewen et al.
in 2013.
Gorgosaurus is classified in the theropod subfamily Albertosaurinae within the family Tyrannosauridae. It is most closely related to the slightly younger Albertosaurus. These are the only two definite albertosaurine genera that have been described, although other undescribed species may exist. Appalachiosaurus was described as a basal tyrannosauroid just outside Tyrannosauridae, although American paleontologist Thomas Holtz published a phylogenetic analysis in 2004 which indicated it was an albertosaurine. More recent, unpublished work by Holtz agrees with the original assessment. All other tyrannosaurid genera, including Daspletosaurus, Tarbosaurus and Tyrannosaurus, are classified in the subfamily Tyrannosaurinae. Compared to the tyrannosaurines, albertosaurines had slender builds, with proportionately smaller, lower skulls and longer bones of the lower leg (tibia) and feet (metatarsals and phalanges).
The close similarities between Gorgosaurus libratus and Albertosaurus sarcophagus have led many experts to combine them into one genus over the years. Albertosaurus was named first, so by convention it is given priority over the name Gorgosaurus, which is sometimes considered its junior synonym. William Diller Matthew and Barnum Brown doubted the distinction of the two genera as early as 1922. Gorgosaurus libratus was formally reassigned to Albertosaurus (as Albertosaurus libratus) by Dale Russell in 1970, and many subsequent authors followed his lead. Combining the two greatly expands the geographical and chronological range of the genus Albertosaurus. Other experts maintain the two genera as separate. Canadian paleontologist Phil Currie claims there are as many anatomical differences between Albertosaurus and Gorgosaurus as there are between Daspletosaurus and Tyrannosaurus, which are almost always kept separate. He also notes that undescribed tyrannosaurids discovered in Alaska, New Mexico and elsewhere in North America may help clarify the situation. Gregory S. Paul has suggested that Gorgosaurus libratus is ancestral to Albertosaurus sarcophagus.
Below is the cladogram of Tyrannosauridae based on the phylogenetic analysis conducted by Loewen et al. in 2013.
Gorgosaurus