Stance detection is the task of inferring for/against attitudes towards a particular target from text. As targets are in principle unlimited, however, research in the field has moved from so-called in-domain classification (which assume the availability of a sufficient number of stances towards the intended target for training purposes) to more realistic zero-shot scenarios. However, regardless of which - or how much - training data is taken into account, most existing zero-shot approaches are devoted to the English language, in stark opposition to alternatives devoted to Portuguese. As a means to overcome some of these difficulties, this article presents a benchmark (hereby understood as the combination of a dataset, baseline systems and their results) for zero-shot Portuguese stance detection that is, to the best of our knowledge, the first of it kind. More specifically, we adapt a number of existing models available for the English language to Portuguese, and introduce novel approaches to the task based on more recent prompt engineering methods and off-task labelling, achieving SOTA results that are, in some cases, even superior to in-domain classification.