Purpose - The purpose of this paper was to explore the role knowledge sharing plays in both firm-sponsored (FS) and user-generated (UG) Online Brand Communities (OBCs) on Facebook. Branding through online mediums is an under-researched area that is slowly gaining attention in the literature. In some ways, action has come first as theory struggles to catch up with technological advances. Given that social sharing behaviours (i.e. online social networking) are arguably driving the strategic direction of marketers, it is important to understand the discourse that is being communicated. One such avenue is through participation in an OBC. While it is apparent that research is growing in the OBC area, there are still areas of interest that have gained little attention. Design/methodology/approach - Data were collected using netnography, an appropriate yet under-applied methodological technique used to investigate the consumer behaviour of cultures and communities present on the Internet. Specifically, Facebook Pages relating to five OBCs based on the cruise-liner P&O Australia have been chosen for this case study. Findings - Results indicate that in both the FS and UG OBCs, knowledge-sharing was seen to have an important influence on pre-purchase decision-making. It also acted as a mechanism for trust building and sharing brand experiences and as an important encouragement to developing a sense of community among community members. A particularly interesting outcome of this research was the way in which consumers have taken on an active role in co-creating brand identity, which seemingly illuminates the role of brand management in social media. Practical implications - Given that this research was conducted with a real brand, with real customers, in a real OBC, the findings also point to some important practical applications. This study has found that the role of brands in their online forums is paramount, and as such, highlights the importance of effective brand governance. The rise of technology brings increased opportunities for a brand to reach out to their consumers. This study makes a further contribution by providing insights into how the consumer- brand relationship is shaped by the communication that occurs between consumers. To this end, consumers see it as the brand’s responsibility to monitor such online platforms, thus indicating the management of OBCs needs to be at the forefront of brand management practices. Originality/value - This study represents one of the earliest investigations of brand communities facilitated by social media, specifically focusing on Facebook as the communication platform. Importantly, this study increases our knowledge of consumer interaction in social media, with an emphasis towards the role that knowledge sharing contributes to OBCs and the differences prevalent between FS and UG online communities.