Sierra is a fictional character portrayed by Dichen Lachman in the Fox science fiction series Dollhouse, created by Joss Whedon. Within the series' narrative, Sierra is an "Active" or a "doll", one of a group of men and women who can be programmed with memories and skills to engage in particular assignments; in their default state, Actives are innocent, childlike and suggestible. Before having her memories wiped, Sierra's name was Priya Tsetsang. Although Sierra does not exhibit the same self-awareness that Echo has, she develops feelings such as love in her doll state.

Dichen Lachman is an Australian actress and model. She earned recognition starring as Katya Kinski in the soap opera Neighbours (2005–2007) and as Sierra in Joss Whedon's science fiction drama series Dollhouse (2009–2010).