A boom in the availability of data provides a substantial opportunity for both researchers and practitioners to find new insights and previously unseen patterns from data, detect anomalies and also increase and improve levels of service to people. The use of big data is emerging in various fields of research, including in tourism. This chapter provides an overview of the use of big data in tourism practice and research. A particular focus is on social media data, as this is of high value to tourism destinations and businesses. Various types of big data analytics are discussed and tourism-relevant examples are provided. The chapter concludes with some critical remarks on the limitations of big data