Sentiment analysis research is an important branch of natural language processing. In the context of global information globalization, sentiment analysis has gradually expanded from single-language to multilingual scenarios. This book is divided into two parts: the first part focuses on single-language sentiment analysis, while the second part delves into multilingual sentiment analysis. It aims to clarify what sentiment analysis is, how to approach single-language and multilingual sentiment analysis, the theoretical foundations, technical basis, and model foundations required for sentiment analysis, available language resources for multilingual sentiment analysis, and future development of multilingual sentiment analysis. This book provides introductory theories, guidance, and technical references for researchers, practitioners, and graduate students in the fields of multilingual natural language processing and sentiment analysis.