This chapter introduces the overall concept of multimedia Quality of Experience (QoE) over the Internet. It presents all the elements of multimedia QoE ecosystem and emphasizes their roles in determining the user satisfaction. The chapter also presents different multimedia transmission components and how these components contribute to successful transmission of the media content. In addition, some key performance indicators relevant to the multimedia QoE are presented with more emphasis on network and application level indicators. Furthermore, different QoE estimation methods and techniques along with QoS/QoE learning algorithms are presented. Finally, the chapter includes some of the future challenges and issues related to multimedia QoE