Activity theory (AT) focuses on how culture and history shape individual consciousness and the organization of collective activity. Its roots lie in Marxist philosophy and the Soviet psychology of the 20th century. Like Marxist philosophy, AT foregrounds the role of material, goal-directed activity in shaping human consciousness. The core ideas of AT trace their origins to the writings of Lev Vygotsky and his followers in the early 20th century, including A. N. Leont’iev, Alexander Luria, Vassily Davydov, S. L. Rubinstein, and P. I. Zinchenko. Current AT focuses on the importance of accounting for multiple and interacting activity systems and partially shared objects.