Speaker sex and gender leave a robust acoustic signature in spoken language. In this chapter, we discuss how the articulatory, acoustic, and perceptual characteristics of speech vary as a function of individuals' biological sex, and of their gender, specifically, their gender identity, gender expression, and participation in different communities of practice. We describe the anatomical and physiological differences between male and female vocal tracts that give rise to differences in the acoustic-phonetic features of male and female speech. We discuss the state of the art in acoustic-articulatory modeling, illustrating the new insights gained from these models, in addition to their current limitations. Beyond anatomy and physiology, we describe the speech patterns that are the consequence of learned social and cultural practices in speech communities, rather than being attributable to sexual dimorphism within our species. This chapter is careful to take a developmental perspective, to illustrate the timescales of the acquisition of both inherently biological and learned, gendered speech patterns. Finally, this chapter takes special care to emphasize the consequences of sex- and gender-based differences on the perception of spoken language. The literature on speech perception reveals how listeners perceptually compensate for male-female differences, while using their expectations about typical male and female speech patterns to navigate through the immense phonetic variation rooted in speaker sex and gender.