It can be considered the most systemic, deadly, and all-encompassing form of institutional violence that currently exists: speciesism, the oppression and exploitation of other animals. For most people on our planet, speciesism is something completely normalized, justified, and encouraged through many facets of dominant cultures. The field of critical/political animal studies, and other fields that challenge anthropocentrism, have already thoroughly problematized, questioned, and analyzed speciesist practices, but one topic receives little academic attention: what can a counter-concept to speciesism contain, without saying what it is not? This thesis is concerned with imagining ‘multispecies worldings’, with the goal to construct positive rather than negative aspects of a counter-concept to speciesism. Instead of offering a single answer, this work illustrates how additive knowledges regarding the possible meanings of ‘multispecies worlding’ make worlds richer. These knowledges emerge through a repertoire of world-making practices with other animals in which we recognize and engage with the ability to respond to each other. Thereby, this thesis answers to – and builds on – various scholarly and activist discourses, including posthumanism, welfarism, animal liberationism, and is theoretically grounded in feminist epistemologies. With a focus on negotiating possibilities, this dissertation is also a work of interaction design. The design practice involves tracing and negotiating multispecies responses with other animals and expressing those narratives as a design research program. These responses are presented as a Multispecies Bestiary, in which ten protagonist animals guide the reader through a collection of big-enough multispecies stories. The thesis thereby illustrates how humans can – together with other animals – find possible meanings of ‘multispecies worlding’ not as a single (broken) solution, but as ever-expanding directions that can permanently unsettle and unmake the established speciesist order.