比较政治学（comparative politics）是政治学的一个分支学科。是利用比较的方法研究政治现象的一门学科，一般分为作为方法论的比较政治学和作为理论知识的比较政治学。

亚里士多德的《政治学》可视为比较政治学研究的开创之作。近代的比较政治研究发展于文艺复兴和启蒙运动之后，比如托克维尔的《论美国的民主》和《旧制度与大革命》。以后马克斯·韦伯、孔德、涂尔干等的社会科学方法对比较政治学之研究有很大影响。但比较政治学作为一门学科之形成，是到了第二次世界大战以后，代表性的著作有杜瓦杰（Maurice Duverger）的《政党论》，阿尔蒙德（Gabriel A. Almond）、维巴（Sidney Verba）的《公民文化：五个国家的政治态度和民主制》等。

Comparative politics is a field in political science, characterized by an empirical approach based on the comparative method. In other words, comparative politics is the study of the domestic politics, political institutions, and conflicts of countries. It often involves comparisons among countries and through time within single countries, emphasizing key patterns of similarity and difference. Arend Lijphart argues that comparative politics does not have a substantive focus in itself, but rather a methodological one: it focuses on "the how but does not specify the what of the analysis." In other words, comparative politics is not defined by the object of its study, but rather by the method it applies to study political phenomena. Peter Mair and Richard Rose advance a slightly different definition, arguing that comparative politics is defined by a combination of a substantive focus on the study of countries' political systems and a method of identifying and explaining similarities and differences between these countries using common concepts. Rose states that, on his definition: "The focus is explicitly or implicitly upon more than one country, thus following familiar political science usage in excluding within-nation comparison. Methodologically, comparison is distinguished by its use of concepts that are applicable in more than one country."