The chapter aims to explore the application of graph theory and networks in the recommendation domain, encompassing the mathematical models that form the foundation for the algorithms and recommendation systems developed based on them. The initial section of the chapter provides a concise overview of the recommendation field, with a particular focus on the types of recommendation solutions and the mathematical description of the problem. Subsequently, the chapter delves into the models and techniques for utilizing graphs and networks, along with illustrative examples of algorithms constructed on their basis.