The emergence of the Internet has given rise to e-leaders of opinion, influential individuals on social networks whose sphere of influence expands thanks to their online presence. Companies, aware of their power, are integrating them into their marketing strategies to stimulate consumer engagement with brands. However, academic literature remains divided on the specific characteristics of opinion e-leaders. The aim of this book is to define their profile and model their impact on consumer engagement. The methodology adopted begins with an exploratory netnographic study on Facebook, conducted on the page of an opinion e-leader, supplemented by qualitative interviews with the page's subscribers. This was followed by a confirmatory phase based on a quantitative survey of 318 Internet users. The proposed model aims to better understand the influence of these leaders on online consumer behavior.