Werewolves, also known as Lycanthropes and the Children of the Moon, are a species of Downworlders.
Like vampires, werewolves are humans infected with a demonic disease—Lycanthropy in their case—which gives them the ability to transform into powerful wolves, Changing either under the influence of the full moon or at will. In their lupine and human forms, werewolves possess inhuman strength, speed, and other enhanced capabilities, with strong claws and canines.
Werewolves are also able to Change partially, "half in and half out of wolf form", with their wolf ears, taloned hands, muzzle, and some fur, but giving them the ability to speak. While Turned, they can bear a little bit of resemblance to their human selves through their coat's color or pattern, though their eyes become that of a wolf's; their eye color changes to either blue, or a bright color ranging from yellow or yellow-green, to orange or gold. They also develop much sharper senses, able to see, hear, and smell very good. A werewolf's eyesight problems also improves when in their wolf form, though the defect returns while in human form.
In addition to their supernatural strength, grace, and reflexes, werewolves have the same unnaturally accelerated healing abilities as most other Downworlders. They cannot regenerate a severed limb, but they can recover quickly from most mundane wounds.
In human form, they look like they would as mundanes, and retain their superhuman capabilities. Werewolves are also mortal; they age and die normally like ordinary humans, though they do grow slightly faster.
With their keen senses, werewolves can still see well at night or in dark places, much like vampires. 
When werewolves grow old, they still retain much of their physical strength. Even werewolves that have reached a very old age can still be strong enough to fend off a Shadowhunter. 
It is unknown what demon created werewolves, or even when exactly they first appeared. It was a belief, however, that the demon that passed on the disease to humans was mortal enemies with the one that gave birth to vampires, which is believed to be Hecate. It is believed that lycanthropy first appeared in the forests of Central Europe in the 13th century, spread rapidly through Europe, then more slowly to the rest of the world.
Persecuting and publicly burning werewolves was prevalent in the late 15th century and early in the 16th century.
Humans are Turned when bitten or scratched by a werewolf; though not all bitten or scratched are Turned, this still cause lycanthropy in its victim approximately half of the time. In modern times, many safeguards and organizational work by Shadowhunters and by werewolves themselves against werewolf bites are in place, so rogue werewolf bites are said to be a rare occurrence now.
Werewolves can also be Turned through a spell, and can also be born from two werewolf parents, though not all children of werewolves will necessarily be born with lycanthropy. The child of a mundane and a werewolf has a chance of being infected, but they may also fight off the infection in the womb, thus resulting in a mundane child, while the offspring of two werewolves may or may not become a werewolf. If the child is born an ordinary human, they would bear a few un-ordinary properties. Half- or part-werewolves—or those with the dormant virus—have increased speed and strength and can pass on the virus, but can never Turn into actual wolves.
For new werewolves, the first few years are crucial for their development and discipline. The demon strain that causes lycanthropy causes various changes, such as waves of uncontrollable aggression, inability to control rage, suicidal anger and despair, especially among those with no support from a pack. When overwhelmed, many of them turn violent—against others or against themselves, leading to a high suicide rate and a high rate of domestic violence. Most rogue werewolves in cities are also shot by cops, and those in the woods or on farms starve or die in fights with bears, etc.
With self-possession and proper training to control themselves and their transformations, werewolves can easily adjust and live among mundanes peacefully without detection, more so than other Downworlders. After the first transformation, it takes a werewolf some time to be able to resist the effect of the moon in its different phases. Many lycanthropes, like Luke Garroway, train themselves to be impervious to the effects of the moon during most of its phases, but even well-trained ones like Luke are still forced into their wolf form during a full moon.
The only ways to permanently wound or kill a werewolf are either through a seraph blade or with pure silver. Silver is associated with the moon, and wounds made with silver weapons will not only cause permanent damage to the wounded but will also cause them great pain, as even their enhanced healing abilities are not effective when a wound is inflicted by silver. Institutes have a cache of silver weapons in place for just this reason.
Many werewolves, like vampires, belong to a group: in their case, a pack. There are also some packless wolves, and those tend to travel alone at night, keeping to the byways and country roads. The Praetor Lupus is in charge of ensuring that all new Downworlders find their place in their respective society, including finding packs for orphaned werewolves.
Each werewolf pack is lead by an alpha wolf. Any werewolf that kills the pack leader will subsequently gain control of the pack. Aside from battle, a werewolf leader can also simply depart and name a new one to replace him/her.
As werewolves, they follow the long held tradition of being mortal enemies of vampires. Maia Roberts explained that the belief is that the demons who passed on the disease to humans that gave birth to vampires and werewolves had been mortal enemies, and, as a result, the prejudice was passed down through their respective races.
- Wolfsbane is a plant known to have a negative effect against werewolves in various lores, but it is unknown what wolfsbane does to werewolves in the Shadowhunter Chronicles. The werewolf Jordan Kyle was known to have been growing them on his balcony, and werewolves buy them from the Shadow Market. Simon noticed Jordan's wolfsbane and once commented on the fact that it had silvery leaves.
- Refined sugar is supposedly harmful to werewolves.
- Their clothes are torn off whenever they Turn.
- While it has been established that it is possible for a werewolf to be born infected with lycanthropy, the Shadowhunter's Codex states that werewolf parents do not pass lycanthropy to their children. This may, however, be due to the fact that the Codex contains mostly knowledge earned by the Shadowhunters, and that most of them simply do not know or believe this.
- To become a werewolf, a mundane must be bitten. But the biting werewolf doesn't have to be transformed. This is how Jordan became a werewolf after a werewolf bit him in his human form. 
- Officially, it is said that the probability of becoming a werewolf after a bite is fifty percent. However, Joyce is of the opinion that the probability is closer to seventy-five percent. 
- Jace once mentions that werewolves occasionally hunt demons. However, this was only addressed once and then never taken up again. 
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 City of Bones
- ↑ 2.0 2.1 2.2 2.3 2.4 City of Ashes
- ↑ The Last Stand of the New York Institute
- ↑ Clockwork Prince
- ↑ 5.0 5.1 5.2 5.3 Lady Midnight
- ↑ 6.0 6.1 The Shadowhunter Chronicles
- ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 The Shadowhunter's Codex
- ↑ 8.0 8.1 citation needed
- ↑ City of Lost Souls
- ↑ The Evil We Love
- ↑ 11.0 11.1 11.2 City of Fallen Angels
- ↑ Babies — Cassandra Clare on Tumblr
- ↑ The Course of True Love (And First Dates)
- ↑ City of Heavenly Fire
- ↑ City of Lost Souls
- ↑ Because of the wiki's "series book and Cassie statements trump Codex" rule, the first, being from a series' book, will be the basis of knowledge and will be accepted and considered canon/truth.
- ↑ City of Fallen Angels
- ↑ City of Glass
- ↑ City of Bones