- Dûr-edain: High-Man-Uruk-hai Crossbreed of Isengard
- Drû-Uruks: Wild Man-Snaga-Uruk-hai Crossbreed of Isengard
- feral Uruk-hai: savage, wild Uruk-hai, probably descendants of uncontrolled breeding or Uruks escaped from Sauron's pits
- Gusmûras: intermediate form or crossbreed of early Uruk and lesser Orc
- Kû-Uruk: elder bloodlines of Greater Orcs or Hobgoblins before the first Black Uruks of Mordor appeared, who were supposedly bred from the elder Kû-Uruk strain which appeared about TA 1600.
- Mordor Uruk-hai or Black Uruks: the Uruk-hai of Sauron, introduced in TA 2475
- Scara-hai: a tribe of early Uruks with shapeshifting ability (Uruk-Werewolf Crossbreeds)
- Fighting Uruk-hai or Great Uruks (Uruk-hai perfected): the late Uruk Breed of Isengard, Uruk-hai with traces of Goblin-man-blood, fully immune to sunlight but unable to see in the dark
- Uruk-Warg-Riders: a smaller breed of perfected Uruk-hai or Half-Orcs employed as elite Wargriders (see Sharkû the Orc)
Uruks of renown
Uruk-hai of Mordor
Uruk-hai of Isengard
The Uruk-hai may have been bred out of captured and magically altered Dúnedain and Black Númenoreans. Alternatively, they could be the much worn-down descendants of Boldogs, having been bred with ordinary Orcs so many times that they were shadows of their ancestors. They could also be a combination of the two, being descended from both the Númenoreans and Boldogs. In fact, considering how different the Uruk-hai of Isengard seem to be from the Uruk-hai of Mordor (one example being that the Uruk-hai of Isengard cannot see as well during daylight), it's possible that different Uruk-hai have different amounts of diverse ancestry, For example, the Isengard Uruk-hai are perhaps more human in ancestry, or at least less magically altered human ancestry (in contrast from Uruk-hai who are presumably descended from either magically altered humans, Boldogs, or both), which may suggest that Isengard Uruk-hai aren't in fact pure Uruk-hai, if there were even such a thing, and would count more as Dur-Adan half-Orcs.