Lycanthropes are sentient beings that have been afflicted with Lycanthropy, the ability (albeit typically involuntary) to transform into a large, humanoid animal. There are eight referenced types of lycanthropes throughout Tamriel.
Types of lycanthropes
Werebears
The Werebear is believed to exist in Skyrim, supposedly as the most common type of lycanthrope in Skyrim. Although they also appear on the island of Solstheim, this could potentially be due to the close proximity of the locations or the date at which the text making such an inference was written in. The idea is derived from the fact that Solstheim previously belonged to Skyrim. During the events of The Elder Scrolls V: Skyrim, luckily no Werebears can be found, as they exist only on Solstheim. In addition to that, the Dragonborn cannot become a Werebear despite their inclusion.
Werewolves
The Werewolf is the only lycanthrope known to exist everywhere in Tamriel. They are confirmed to have a connection with the Daedric Prince Hircine, and are often described as his hounds. Although they are the second most common lycanthrope in Skyrim, following Werebears, the Werewolf transformations are oddly absent from Morrowind (until the Bloodmoon DLC) and Oblivion, despite being in every other canon game in the series.
The Circle, an elite group of warriors within The Companions, is comprised of werewolves. Lycanthropy is passed down to new members through a blood ritual upon their admittance into the Circle.
Werewolves carry a weakness towards Silver Weapons.
Werecrocodiles
Werecrocodiles exist in Black Marsh and southern Morrowind. Argonians are the only known race that can become one of them.
Werelions
Werelions have been spotted in Black Marsh, Cyrodiil, and the wetter regions of Elsweyr. They are said to be quite common, despite never being seen in the Elder Scrolls Online or even Oblivion.
Werevultures
Werevultures exist mainly in Valenwood and are rarely mentioned in the canon series.
Wereboars
Wereboars can be discovered in both High Rock and Hammerfell. They are the third Lycanthropes, along with Werewolves and Werebears, to appear in the series.
Weresharks
Weresharks are believed to roam the oceans around Tamriel. Their existence has never been confirmed, as only a rumor of their existence is ever mentioned such as in Daggerfall text: On Lycanthropy and even then the author, Varnard Karessen, only briefly mentions that he has heard of these lycanthropes, and in Skyrim when M'aiq the Liar will mention a brief encounter with one near water.
Werebats
Werebats sometimes serve as guardians to Vampire clans, and are commonly found in Valenwood. They were first seen in the Elder Scrolls Online.