Network theory has become an important branch of research in the social sciences. It applies to any system of entities and their relationships including friendship networks, inter-firm alliances, citations between texts, transportation flows between airports, trade flows between countries, et cetera. In urban geography, network theory has become a central tool in analysing global dependencies between cities inspired by seminal works by Manuel Castells (on space of flows versus space of places) and Saskia Sassen (on world cities). Here, the main question is what determines that some cities are well-connected in global networks and others are not. In economic geography, applications of network theory include the effect of business networks on firm performance and the debate on whether 'social capital' is conducive for entrepreneurship or not. In transport geography, network theory is used to analyse hub-and-spoke systems as well as the optimal design of transportation systems. This course aims to provide an overview of the core topics in geography regarding networks and to teach students how to apply network concepts in an empirical research design, which includes data collection, network visualisation and network analysis.