Acorna is a "Unicorn Girl", a fantasy fiction character created by Anne McCaffrey and Margaret Ball in their novel Acorna: The Unicorn Girl (1997). Acorna is also one name for the Acorna Universe series: ten fantasy or science fiction novels by McCaffrey and Ball (the first two) or McCaffrey and Elizabeth Ann Scarborough (eight more, 1999 to 2007). The Acorna series is a sub-set of the Federated Sentient Planets Universe. Other sub-sets include the Crystal Singer series, the Brain and Brawn Ship series and the renowned Dragonriders of Pern series, all predominantly authored by Anne McCaffrey. Other contributors to the Acorna series include Jody Lynn Nye, Lyman Frakoss, Roman R. Ranieri and Mickey Zucker Reichert.