This dissertation proposes a form of collaboration between legal and economic research called Minimalist Law-and-Economics. This approach acknowledges the core commitments of both disciplines and promotes a division of labour based on their comparative advantages. While lawyers expect an analysis that is grounded in legal reasons and respectful of the fairness and wrongfulness theses, economists expect efficient market relations, analysed from an ‘ex-ante’ perspective respectful of epistemological and normative minimalism. The collaboration proposed in this dissertation improves the lawyers’ understanding of market relations and thus enhances their ability to regulate them effectively. Conversely, economists can strengthen the empirical foundations of their research by considering legal reasons as evidence. This is attractive for value choices especially, since their justification is not central to economists’ expertise. To support Minimalist Law-and-Economics, this dissertation warrants three claims: 1) the economic claim holds that consumer welfare is a maxim and used in market efficiency analysis in alternative to total welfare; 2) the translation claim holds that with consumer welfare rather than total welfare as the maxim and, it is possible to offer a plausible economic account of fair market relations; and 3) the doctrinal claim holds that the efficiency hypothesis, which has consumer welfare as maxim and, explains the reasons given in EU antitrust and consumer law better than the traditional efficiency hypothesis based on total welfare. The dissertation is divided into three parts. Part I clarifies the conditions for collaboration considered by Minimalist Law-and-Economics. Part II builds the theory that warrants the economic and translation claims. To do this, it gives an account of market relations that are compatible with the fairness and wrongfulness theses and the ‘ex-ante’ perspective. Part III narrows the focus to EU antitrust and consumer law in order to warrant the doctrinal claim and to show how the analysis of legal reasons can be epistemologically and normatively minimalist. United in diversity, economic and legal research may well have a brighter future.