A knowledge graph is a knowledge base that uses a graph-structured data model or topology to integrate knowledge and data. Knowledge graphs are often used to store interlinked descriptions of entities — real-world objects, events, situations or abstract concepts — with free-form semantics, not fitting into a single traditional ontology.

Since the development of the Semantic Web, knowledge graphs are often associated with linked open data projects, focusing on the connections between concepts and entities. The are also prominently associated with and used by search engines such as Google, Bing, and Yahoo; knowledge-engines and question-answering services such as WolframAlpha, Apple’s Siri, and Amazon Alexa; and social networks such as LinkedIn and Facebook.