研究所，中国大陆及澳门称研究生院、**称研究所、香港称研究院（美国通常称为Graduate Schools、英国及其他英语国家称为 Postgraduate Schools、日本称为「大学院」（大学院）），是本科之后的高端教育研究机构，一般设于大学中，以「某大学某研究所」的形式存在，也有独立设立者。研究所需大学毕业及同等学历才能取得报考或申请入学资格，主要为培养硕士、博士人才及进行基础研究工作，许多大学教授也会在研究所开课并领导研究工作。

研究所与专业学院（Professional Schools）有一定的分别。研究所不一定培训某个行业的人才，但专业学院则旨在培养具有专业资格的人才（如医学院和法学院）。在美国及加拿大，某些专业学院的所有课程一般都需要申请者先取得一个本科学位方可报读，如美加的医学院，即便是医学本科课程均只收本科毕业生，因此它们也常被直接归为是研究所的一种。

A graduate school (sometimes shortened as grad school) is a school that awards advanced academic degrees (i.e. master's and doctoral degrees) with the general requirement that students must have earned a previous undergraduate (bachelor's) degree with a high grade point average. A distinction is typically made between graduate schools (where courses of study vary in the degree to which they provide training for a particular profession) and professional schools, which offer specialized advanced degrees in professional fields such as medicine, nursing, business, engineering, or law. The distinction between graduate schools and professional schools is not absolute, as various professional schools offer graduate degrees (e.g., some nursing schools offer a master's degree in nursing). Also, some graduate degrees train students for a specific profession (e.g. an MSc or a PhD in epidemiology trains a person to be an epidemiologist).