Spontaneous resting-state fluctuations in neuronal activity offer insights into the inherent organization of the human brain, and may provide markers for diagnosis and treatment of mental disorders. Resting state functional magnetic resonance imaging (fMRI) can be used to investigate intrinsic functional connectivity networks, which are identified based on similarities in the signal measured from different brain regions. From data acquisition to interpretation of results, Introduction to Resting State fMRI Functional Connectivity discusses a wide range of approaches without requiring any previous knowledge of resting state fMRI, making it highly accessible to readers from a broad range of backgrounds. Supplemented with online datasets and examples to enable the reader to obtain hands-on experience working with real data, this primer provides a practical and approachable introduction for those new to the field of resting state fMRI. The Oxford Neuroimaging Primers are short texts aimed at new researchers or advanced undergraduates from the biological, medical or physical sciences. They are intended to provide a thorough understanding of the ways in which neuroimaging data can be analyzed and how that relates to acquisition and interpretation. Each primer has been written so that it is a stand-alone introduction to a particular area of neuroimaging, and the primers also work together to provide a comprehensive foundation for this increasingly influential field.