<p>Self-determination theory proposes that various types of motivation (intrinsic, integrated, identified, introjected, external, and amotivation) follow a continuum. This continuum structure is presumed to be universal, and considerable past research has supported its existence across diverse populations. In the current study, we provide the first piece of evidence for the existence of heterogeneity in the continuum structure between subpopulations. Factor mixture modeling (FMM) was performed on the academic motivation of a large sample of American college students (<i>N</i> = 18,875). The generalized FMM supported the existence of three classes: Class 1 generally supported the continuum (<i>N</i> = 10,188), and was named the Normative class; Class 2 (<i>N</i> = 4,521) showed an all-positive correlation matrix between motivations, without supporting the continuum pattern, and was named Careless Respondents. Class 3 (<i>N</i> = 4,166) generally supported the continuum with the important exception that external motivation was weakly associated with other motivations. We named Class 3 Weakly Associated External, and speculated that these were students whose external motivation may be determined mainly by salient external constraints rather than their individual self-determination. These interpretations were supported by multidimensional scaling and other follow-up analyses based on posterior classification results.</p>