The red-billed streamertail, also known as the doctor bird, scissor-tail or scissorstail hummingbird, is a unique species. The male has an iridescent emerald-green body plumage that appears slightly darker on the back. Its flight feathers on the sides are dark brown to black while the forked tail has long second outermost streamers, which are only second in length to those of the black-billed streamertail. When perched, the streamers cross over each other. The head is black with elongated lateral crown feathers and ear coverts extending beyond the nape of its neck.

The female bird has a distinct appearance with a white throat, chest, and belly combined with green upperparts. Additionally, there are green spots on the sides of her breast. The tail of the female bird has central rectrices that are green while the rest are dark blue with broad white tips. Unlike male birds, the female lacks streamers and has a red bill. Juvenile males have a similar appearance to adult males but they lack streamers as well.

The Red-billed Streamertail can be found exclusively in Jamaica, except for in the far east of the country.