Research concerning the variety of close relationships adults maintain, initiate, cease, and lose during middle and later adulthood has been fast growing in recent decades. Much of the theoretical and empirical work in this field has aimed to overcome views of older age as a time of loss and decline, both individually and socially. Moreover, recent trends have focused on the increasingly diverse experiences of the aging population. This includes not only extended life expectancy – and, importantly, extended healthy life expectancy – but also demographic changes, including larger proportions of racial/ethnic minorities attaining older age; new cohorts of openly LGBTQ adults entering mid and later life, many of whom represent the first generation of same-sex married couples; and the phenomenon of “gray divorce” and romantic repartnering in the years beyond age 50. This chapter will cover both the history and foundations of research on close relationships in middle and later life, as well as these recent trends in the field, finishing with an eye toward future directions as both the aging population and our perceptions of it continue to change.