Arctostaphylos rainbowensis is a rare species in the Ericaceae (Heath) family known by the common name Rainbow manzanita. It is endemic to California, where it is known only from northern San Diego and southern Riverside Counties. A specimen was first collected in 1973 and considered to be part of a disjunct population of Arctostaphylos peninsularis, or alternately a hybrid between A. glauca and Arctostaphylos glandulosa. Following phenetic analyses both possibilities were discarded and the plant was described as a new species in 1994. It was named for the community of Rainbow, California, near where it is most common in the chaparral of the lower elevation coastal mountains and the only manzanita species throughout most of its range.

This is an erect shrub reaching a bushlike one meter to a treelike four meters in height. It produces a burl at its base and is coated in reddish brown, smooth bark. The oval leaves are up to 5 centimeters long and 3.5 wide and are hairless and somewhat waxy in texture. The flower cluster is a hanging cluster of white urn-shaped flowers each about 6 to 8 millimeters long. The fruit is about a centimeter wide and ripens to a dark purple-brown.