Multispecies Justice (MSJ) is a theory and practice seeking to correct the defects making dominant theories of justice incapable of responding to current and emerging planetary disruptions and extinctions. Multispecies Justice starts with the assumption that justice is not limited to humans but includes all Earth others, and the relationships that enable their functioning and flourishing. This Element describes and imagines a set of institutions, across all scales and in different spheres, that respect, revere, and care for the relationships that make life on Earth possible and allow all natural entities, humans included, to flourish.