Billina is a hen tossed overboard in a storm with Dorothy Gale in the novel Ozma of Oz, the third Oz book, and a sequel to L. Frank Baum's The Wonderful Wizard of Oz. She is Dorothy's animal companion for this adventure, the role that Toto the dog serves in the first book.
A spunky, talkative chicken, Billina was originally named Bill because, she tells Dorothy, "no one could tell whether I was going to be a hen or a rooster." Dorothy insists on changing the hen's name to a feminine form. Billina endures several scares with Dorothy before defeating the Nome King as only a hen can. At the end of the novel, Billina settles in the Emerald City.