Spectrum sensing, spectrum decision, spectrum sharing, and spectrum mobility are four major functions of Cognitive Radio (CR) systems. Spectrum sensing is utilized to identify primary users’ spectrum occupancy status, based on which CR users can dynamically access the available channels through the regulation processes of spectrum decision, spectrum sharing, and spectrum mobility. To alleviate the processing delays involved in these four functions and to improve the efficiency of spectrum utilization, spectrum prediction has been extensively studied in literature. This paper surveys the state-of-the-art of spectrum prediction in CR networks. The authors summarize the major spectrum prediction techniques, illustrate their applications, and present the relevant open research challenges.