Ixodes is a genus of hard-bodied ticks (family Ixodidae). It includes important disease vectors of animals and humans (tick-borne disease), and some species (notably Ixodes holocyclus) inject toxins that can cause paralysis. Some ticks in this genus may transmit the pathogenic bacterium Borrelia burgdorferi responsible for causing Lyme disease. Additional organisms that may be transmitted by Ixodes are parasites from the genus Babesia, which cause babesiosis, and bacteria from the related genus Anaplasma, which cause anaplasmosis.

Ixodes species have a near-cosmopolitan distribution and occur in all major biogeographic realms, including Antarctica, where they are associated with seabirds and penguin rookeries. The genus parasitizes a wide range of vertebrate hosts worldwide, including mammals, birds, and reptiles. Rodents and passerine birds are among the most commonly recorded hosts, especially in the Americas.

Ixodes is the sole representative of the Prostriata clade of the Ixodidae. Prostriate ticks are distinguished from the Metastriata with reference to the position of the anal groove. In Ixodes species, the groove loops anterior to the anus, whereas in Ambloymma, for example, the groove is positioned posterior to the anus. Ixodes species are small to medium-sized ticks, with a usually pyriform (pear-shaped) or ovate body profile. Mouthparts are anterior in both sexes, but usually long and slender in females, and short in males. Males have sclerotised adanal plates. Ixodes species are eyeless.

Ixodes contains 274 species. Classification, recognition and phylogenetic resolution of the Ixodes subgenera is ongoing. As many as 24 subgenera have been recognised by different authors. All are included here for completeness.

Three fossil species of Ixodes are known from amber deposits ranging from the Cretaceous to the Eocene:

Refer to the following external links for recent changes to Ixodes taxonomy: