This chapter provides an overview of some of the key themes underlying current loneliness research. This includes a discussion of why loneliness has become such a prominent issue in science and in public discourse over the past few years, and whether the attributes and experience of loneliness are similar in young adults and older individuals. I then speculate on how loneliness research is likely to evolve over the next decades, including discussion of the relationships loneliness, isolation, and solitude, and promising developments in technologies that may enhance the measurement of loneliness. Future priorities for research on loneliness and health, and the opportunities provided by developments in biological assessments, are outlined. Finally, I present some thoughts about the challenges of loneliness intervention research and practice.