Neo4j is a graph database management system (GDBMS) developed by Neo4j Inc.

The data elements Neo4j stores are nodes, edges connecting them and attributes of nodes and edges. Described by its developers as an ACID-compliant transactional database with native graph storage and processing, Neo4j is available in a non-open-source "community edition" licensed with a modification of the GNU General Public License, with online backup and high availability extensions licensed under a closed-source commercial license. Neo also licenses Neo4j with these extensions under closed-source commercial terms.

Neo4j is implemented in Java and accessible from software written in other languages using the Cypher query language through a transactional HTTP endpoint, or through the binary "Bolt" protocol. The "4j" in Neo4j is a reference to its being built in Java, however is now largely viewed as an anachronism.

Neo4j is developed by Neo4j, Inc., based in San Mateo, California, United States and Malmö, Sweden.

Version 1.0 was released in February 2010.

Neo4j version 2.0 was released in December 2013.

Neo4j version 3.0 was released in April 2016.

In November 2016, Neo4j successfully secured $36M in Series D Funding led by Greenbridge Partners Ltd.