等级线性模型（Hierarchical Linear Model、简称 HLM）也称为mixed-effect model,random-effect models或者multilevel linear models，是一种复杂的统计模型。在计量经济学文献中也常常被称为Random-coefficient regression models(Rosenberg, 1973; Longford, 1993)。在某些统计学文献种也被称为Covariance components models(Dempster, Rubin, & Tsutakawa, 1981; Longford, 1987)。现在广泛被使用的名称Hierarchical Linear Model最早出现于1972年Lindley and Smith的论文以及1973年Smith的论文。

Multilevel models (also hierarchical linear models, nested models, mixed models, random coefficient, random-effects models, random parameter models, or split-plot designs) are statistical models of parameters that vary at more than one level. An example could be a model of student performance that contains measures for individual students as well as measures for classrooms within which the students are grouped. These models can be seen as generalizations of linear models (in particular, linear regression), although they can also extend to non-linear models. These models became much more popular after sufficient computing power and software became available.