Speciesism is a concept that was derived to name forms of discrimination and oppression against nonhuman animals that could be compared to racism and sexism. The concept was formulated in strong terms by Richard Ryder, Peter Singer, and Tom Regan (in turn buttressed by the work of Van Potter, Hans Ruesch, Rachel Carson and others) that made it a powerful tool for social and political movements. The discourse on speciesism has been amplified and changed by a set of newer writings in the last few decades that take a more ethological, critical theory, and deconstructive bent. This paper outlines some of the conditions for an antispeciesism based on posthumanism. As humanism itself is the most virulent form of speciesism, no robust antispeciesism can be developed without continued challenge to humanism (which remains a central element in much of the thinking on speciesism, including its most prominent formulations).