This article examines what constitutes a 'good' mathematical problem and proposes to conceptualize the notion of "collective mathematical problems" as phenomena that arise through and by way of the inter-actions enabled by the collective itself. The author examines how these collective mathematical problems can emerge in the classroom while (re)positioning them in relation to the notion of 'good' mathematical problem for the classroom. These inter-actions and changes unfold within a loop of mutual influence, wherein each continuously shapes the development of the other. This dynamic invites consideration of the classroom not as a mere collection of individuals acting side by side, but as a collectivity that moves forward through re-actions with one another, and where the actions of some open up new possibilities for action for others. [This article is available online only.]