Ectoparasites of horses include arachnids and insects. Throughout the world they are responsible for serious damage although this is rarely the case in New Zealand.

Ticks tend to be more active in summer months in warm areas while mites and lice are more frequently encountered during winter months in cooler climates. Damage caused by ectoparasites includes worry, skin damage, and the transmission of disease organisms.

Ectoparasites of economic significance to horses are listed in the following section. Other ectoparasites of minor importance or which are restricted to limited geographic areas are listed after the descriptions.