信誉系统是一种通过一些实体相互给出看法和评价，来试图确定这些实体的等级和类别的合作性筛选算法。

这很类似于一种推荐系统, 但是和其他对实体的推荐不同（比如书籍、电影，或者是音乐），信誉系统是实体间的互相推荐。信誉系统可以使所谓的信任（Resnick 等人 2000）更容易被量化，随着信誉的更加明显，这一系统也变得更加有效。

信誉系统对于大型在线社区是很有用的，用户经常有机会和之前毫无经验的用户互动，也有像YouTube和Flickr这样发布用户生成内容的社区。在那样的环境下，基于信誉系统来决定是否和有经验的用户进行互动是很有帮助的。

A reputation system computes and publishes reputation scores for a set of objects (e.g. service providers, services, goods or entities) within a community or domain, based on a collection of opinions that other entities hold about the objects. The opinions are typically passed as ratings to a central place where all perceptions, opinions and ratings can be accumulated. A reputation center uses a specific reputation algorithm to dynamically compute the reputation scores based on the received ratings. Reputation is a sign of trustworthiness manifested as testimony by other people. New expectations and realities about the transparency, availability, and privacy of people and institutions are emerging. Reputation management – the selective exposure of personal information and activities – is an important element to how people function in networks as they establish credentials, build trust with others, and gather information to deal with problems or make decisions.