Meta-knowledge or metaknowledge is knowledge about knowledge.

Some authors divide meta-knowledge into orders:

• zero order meta-knowledge is knowledge whose domain is not knowledge (and hence zero order meta-knowledge is not meta-knowledge per se)
• first order meta-knowledge is knowledge whose domain is zero order meta-knowledge
• second order meta-knowledge is knowledge whose domain is first order meta-knowledge
• most generally, ${\displaystyle n+1}$ order meta-knowledge is knowledge whose domain is ${\displaystyle n}$ order meta-knowledge.

Note that other authors call zero order meta-knowledge first order knowledge, and call first order meta-knowledge second order knowledge; meta-knowledge is also known as higher order knowledge.

Meta-knowledge is a fundamental conceptual instrument in such research and scientific domains as, knowledge engineering, knowledge management, and others dealing with study and operations on knowledge, seen as a unified object/entities, abstracted from local conceptualizations and terminologies. Examples of the first-level individual meta-knowledge are methods of planning, modeling, tagging, learning and every modification of a domain knowledge. Indeed, universal meta-knowledge frameworks have to be valid for the organization of meta-levels of individual meta-knowledge.

Meta-Knowledge may be automatically harvested from electronic publication archives, to reveal patterns in research, relationships between researchers and institutions and to identify contradictory results.