Younger generations are increasingly questioning the legitimacy of teachers. However, evidence concerning classroom authority and the many factors that shape it tend to disregard the complexity and dynamics of the relationship between the teacher and the student. This paper aims to contribute to further unfold and understand this topic. Specifically, teachers' legitimacy is examined from the scope of the Relational Model of Authority and the principle of autonomy, from the standpoint of the individual (i.e. adolescent's autonomy level) and the individual's perception of the social context (i.e. perceived autonomy support). Participants were 323 adolescents attending two secondary schools in urban areas of Portugal, from 9th to 12th grades. The results indicate that teachers' legitimacy, as recognised by students, varies according to their perceived autonomy support. In addition, more autonomous adolescents, when in contexts that they perceive as lower in autonomy support, recognise lower levels of legitimacy to their teachers, compared with individuals with lower autonomy levels. Results are discussed from the standpoint of the Relational Model of Authority, the Self-Determination Theory and the Theory of Psychological Reactance.