This essay explores the potential of solidarity economy (SE) as theory, practice, and movement, to engender an ontological politics to create and sustain other worlds that can resolve the existential crises of ecological destruction and historic inequalities. We argue that such a politics is necessary to go beyond the world as it is and exceed the dictates of a dominant modernity—capitalism, white supremacy, patriarchy -- that positions itself as the only singular reality -- or One World World (Law 2011). What is needed are alternatives to development in contrast to alternative developments. Over the past decade, the SE movement in Massachusetts has advanced a fight and build approach, which has reframed economy as a matter of concern, as something that communities can, and already do, shape themselves – and that powerfully disrupts the reality of a singular capitalist economy. At the same time, the heterogeneous elements of SE are caught up in and assembling political projects with multiple orientations: modernist, social justice, and ontological (Escobar 2020). SE movement can remain stuck in a modernist politics of growing and scaling businesses and jobs. Even though a social justice approach attends to power and is more amenable to a relational view of reality where things only exist in interconnection, it too can remain mired in One World World liberal politics of redistribution and market ‘solutions’. How SE movement might actualize an ontological politics is a matter of care, an attunement to how relational worlds are coming into being and maintained. As an ontological politics, SE is not about economy qua economy at all, but about creating and sustaining worlds, pluriversal realities where we can be in solidarity with other people, beings, and planetary life systems.