Psychological scientists and laypeople alike have experimented with ways to boost well-being, ranging from changing life circumstances (e.g., buying a new home) to engaging in positive activities (e.g., performing kind acts). This chapter focuses on positive activity interventions (PAIs)—experiments designed to increase positive emotions, meaning, and engagement, as well as to decrease negative emotions—and proposes a taxonomy that organizes these interventions through a social lens. We classify most PAIs based on who is the actor and who is the target. Is the actor the self or another person? Is the target the self or another person? This approach generates four categories of PAIs that may affect the well-being of the participant (i.e., happiness seeker) in different ways, which we have classified into four quadrants: (1) the self-self quadrant, in which the participant is acting on her own behalf (e.g., treating herself); (2) the self-other quadrant, in which the participant is acting prosocially toward another person (e.g., doing an act of kindness); (3) the other-self quadrant, in which the participant is receiving a prosocial act (e.g., expressing gratitude for another’s kindness); and (4) the other-other quadrant, in which the participant witnesses a prosocial act (e.g., feeling elevated upon observing benevolence). We present examples of PAIs from each quadrant and discuss the implications and questions raised by our new taxonomy.