A concept map or conceptual diagram is a diagram that depicts suggested relationships between concepts. Concept maps may be used by instructional designers, engineers, technical writers, and others to organize and structure knowledge.

A concept map typically represents ideas and information as boxes or circles, which it connects with labeled arrows, often in a downward-branching hierarchical structure but also in free-form maps. The relationship between concepts can be articulated in linking phrases such as "causes", "requires", "such as" or "contributes to".

The technique for visualizing these relationships among different concepts is called concept mapping. Concept maps have been used to define the ontology of computer systems, for example with the object-role modeling or Unified Modeling Language formalism.

Concept mapping was developed by the professor of education Joseph D. Novak and his research team at Cornell University in the 1970s as a means of representing the emerging science knowledge of students. It has subsequently been used as a way to increase meaningful learning in the sciences and other subjects as well as to represent the expert knowledge of individuals and teams in education, government and business. Concept maps have their origin in the learning movement called constructivism. In particular, constructivists hold that learners actively construct knowledge.

Novak's work is based on the cognitive theories of David Ausubel, who stressed the importance of prior knowledge in being able to learn (or assimilate) new concepts: "The most important single factor influencing learning is what the learner already knows. Ascertain this and teach accordingly." Novak taught students as young as six years old to make concept maps to represent their response to focus questions such as "What is water?" "What causes the seasons?" In his book Learning How to Learn, Novak stated that a "meaningful learning involves the assimilation of new concepts and propositions into existing cognitive structures."

Various attempts have been made to conceptualize the process of creating concept maps. McAleese suggested that the process of making knowledge explicit, using nodes and relationships, allows the individual to become aware of what they know and as a result to be able to modify what they know. Maria Birbili applied the same idea to helping young children learn to think about what they know. McAleese's concept of the knowledge arena suggests a virtual space where learners may explore what they know and what they do not know.

Concept maps are used to stimulate the generation of ideas, and are believed to aid creativity. Concept mapping is also sometimes used for brain-storming. Although they are often personalized and idiosyncratic, concept maps can be used to communicate complex ideas.

Formalized concept maps are used in software design, where a common usage is Unified Modeling Language diagramming amongst similar conventions and development methodologies.