Klout is a San Francisco-based company that provides social media analytics to measure a user's influence across his or her social network. The analysis is done on data taken from sites such as Twitter and Facebook and measures the size of a person's network, the content created, and how other people interact with that content. The company has been subject to substantial criticism, both for its business model and its operating principle.

Klout scrapes social network data and creates profiles on individuals and assigns them a "Klout score". Klout currently claims to have built more than 100 million profiles. Klout is not an "opt-in" service, but individuals who register at Klout can ensure that all of their social networks are accessed and therefore evaluated in their Klout scores. Klout also builds profiles of individuals who are connected to those who do register at Klout.

Klout scores range from 1 to 100, with higher scores corresponding to a higher assessment by Klout of the breadth and strength of one's online influence. Klout scores are supplemented with three nominally more specific measures, which Klout calls "True Reach", "Amplification", and "Network Impact".