With the rapid development of information technology and the mobile Internet, quickly and accurately mining users’ emotional tendencies toward events and products is essential to grasping social public opinion, adjusting product strategies, and understanding user preferences. Sentiment analysis plays a vital role in this. Especially in recent years, with the development of multimodal sentiment analysis and emotional dialogue, the practical application prospects of sentiment analysis have been further broken through. This chapter systematically introduces sentiment analysis and its methods, mainly including sentiment analysis methods based on sentiment dictionaries, machine learning, and deep learning, and finally gives examples of sentiment analysis applications.