Online behavioral advertising (OBA) is a form of advertising that relies on data about users' behavior (for example clicks, likes, reposts) and uses artificial intelligence to place ads that users may be interested in. The EU heavily regulates OBA, requiring, for example, that companies have users' consent before their surveillance. Yet, the industry is incentivized to acquire consumers' consent by any means necessary, often through manipulation. This thesis builds a framework of manipulation, describes consumer manipulation via OBA, constructs a theory of the harms of this phenomenon, and analyses its boundaries in the EU legal framework.