In algebraic geometry and complex geometry, the Harder–Narasimhan stratification is any of a stratification of the moduli stack of principal G-bundles by locally closed substacks in terms of "loci of instabilities".
In the original form due to Harder and Narasimhan, G was the general linear group; i.e., the moduli stack was the moduli stack of vector bundles, but, today, the term refers to any of generalizations.
The scheme-theoretic version is due to Shatz and so the term "Shatz stratification" is also used synonymously.
The general case is due to Behrend.
This algebraic geometry–related article is a stub.