Feminist psychologists have long posited that relationship authenticity (i.e., the congruence between what one thinks and feels and what one does and says in relational contexts) is integral to self-esteem and well-being. Guided by a feminist developmental framework, the authors investigated the role of relationship authenticity in promoting girls' self-esteem over the course of adolescence. Latent growth curve modeling was used to test the association between relationship authenticity and self-esteem with data from a 5-year, 3-wave longitudinal study of 183 adolescent girls. Results revealed that both relationship authenticity and self-esteem increased steadily in a linear fashion from the 8th to the 12th grade. Girls who scored high on the measure of relationship authenticity in the 8th grade experienced greater increases in self-esteem over the course of adolescence than girls who scored low on relationship authenticity. Further, girls who increased in authenticity also tended to increase in self-esteem over the course of adolescence. The importance of a feminist developmental framework for identifying and understanding salient dimensions of female adolescence is discussed. (Contains 2 tables, 1 figure, and 1 footnote.)