The eastern wolf (Canis lycaon or Canis lupus lycaon), also known as the timber wolf, Algonquin wolf and eastern timber wolf, is a canine of debated taxonomy native to the Great Lakes region and southeastern Canada. It is considered either a unique subspecies of gray wolf, or red wolf, or a separate species from both. Many studies have found the eastern wolf to be the product of ancient and recent genetic admixture between the gray wolf and the coyote, while other studies have found some or all populations of the eastern wolf, as well as coyotes, originally separated from a common ancestor with the wolf over 1 million years ago and that these populations of the eastern wolf may be the same species as or a closely related species to the red wolf (Canis lupus rufus or Canis rufus) of the Southeastern United States. Regardless of its status, it is regarded as unique and therefore worthy of conservation with Canada citing the population in eastern Canada (also known as the "Algonquin wolf") as being the eastern wolf population subject to protection.

There are two forms, the larger being referred to as the Great Lakes-boreal wolf, which is generally found in Minnesota, Wisconsin, the Upper Peninsula of Michigan, southeastern Manitoba and northern Ontario, and the smaller being the Algonquin wolf, which inhabits eastern Canada, specifically central and eastern Ontario and southwestern Quebec, with some overlapping and mixing of the two types in the southern portions of northeastern and northwestern Ontario. The eastern wolf's morphology is midway between that of the gray wolf and the coyote. The fur is typically of a grizzled grayish-brown color mixed with cinnamon. The nape, shoulder and tail region are a mix of black and gray, with the flanks and chest being rufous or creamy. It primarily preys on white-tailed deer, but may occasionally hunt moose and beavers.

In the third edition of Mammal Species of the World published in 2005, the mammalogist W. Christopher Wozencraft listed the eastern wolf as a gray wolf subspecies, which supports its earlier classification based on morphology in three studies. This taxonomic classification has since been debated, with proposals based on DNA analyses that includes a gray wolf ecotype, a gray wolf with genetic introgression from the coyote, a gray wolf/coyote hybrid, a gray wolf/red wolf hybrid, the same species as the red wolf, or a separate species (Canis lycaon) closely related to the red wolf. Commencing in 2016, two studies using whole genome sequencing indicate that North American gray wolves and wolf-like canids were the result of ancient and complex gray wolf and coyote mixing, with the Great Lakes wolf possessing 25% coyote ancestry and the Algonquin wolf possessing 40% coyote ancestry.

In the US, gray wolves including the timber wolf are protected under the Endangered Species Act of 1973, although the protections were removed at the federal level in 2021 before being reinstated in 2022. In Canada, the eastern wolf is listed as Canis lupus lycaon under the Species At Risk Act 2002, Schedule 1 - List of Wildlife at Risk. In 2015, the Committee on the Status of Endangered Wildlife in Canada recognized the eastern wolf in central and eastern Ontario and southwestern Quebec as Canis cf. lycaon (Canis species believed to be lycaon) and a threatened species worthy of conservation. The main threat to this wolf is human hunting and trapping outside of the protected areas, which leads to genetic introgression with the eastern coyote due to a lack of mates. Further human development immediately outside of the protected areas and the negative public perception of wolves are expected to inhibit any further expansion of their range. In 2016, the Committee on the Status of Species at Risk in Ontario recognized the Algonquin wolf as a Canis sp. (Canis species) differentiated from the hybrid Great Lakes wolves which it found were the result of "hybridization and backcrossing among Eastern Wolf (Canis lycaon) (aka C. lupus lycaon), Gray Wolf (C. lupus), and Coyote (C. latrans)".

The first published name of a taxon belonging to the genus Canis from North America is Canis lycaon. It was published in 1775 by the German naturalist Johann Schreber, who had based it on the earlier description and illustration of one specimen that was thought to have been captured near Quebec. It was later reclassified as a subspecies of gray wolf by Edward Goldman.

In the third edition of Mammal Species of the World published in 2005, the mammalogist W. Christopher Wozencraft listed the eastern wolf as a gray wolf subspecies, which supports its earlier classification based on morphology in three studies. This taxonomic classification has since been debated.

In 2021, the American Society of Mammalogists considered the eastern wolf as its own species (Canis lycaon).

When European settlers first arrived to North America, the coyote's range was limited to the western half of the continent. They existed in the arid areas and across the open plains, including the prairie regions of the midwestern states. Early explorers found some in Indiana and Wisconsin. From the mid-1800s coyotes began expanding beyond their original range.