Tristerix is a genus of mistletoe in the family Loranthaceae, native to the Andes, ranging from Colombia and Ecuador to Chile and Argentina. They are woody perennials usually occurring as aerial parasites, are pollinated by hummingbirds and flowerpiercers, with seed-dispersal generally by birds but occasionally by mammals (Dromiciops). The genus is distinguished from other New World Loranthaceae by its simple, terminal, racemose inflorescences, together with its of 4- or 5-merous flowers, versatile anthers, and the presence of endosperm. Further differences include fused cotyledons and the absence of epicortical roots.

Mistletoe is the common name for obligate hemiparasitic plants in the order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they extract water and nutrients from the host plant.