Prior studies of MOOC learners have focused almost exclusively on behavioural and social aspects of engagement. This paper extends the scope of previous studies by adopting a multi-dimensional, person-centred approach to investigate learner engagement in MOOCs. An analysis of 1,452 self-administered survey responses uncovered three prototypical categories of MOOC learners based on patterns of behavioural, cognitive, emotional and social engagement: (1) "Individually Engaged" learners; (2) "Least Engaged" learners; and (3) "Wholly Engaged" learners. The study revealed significant differences among the three cohorts of MOOC participants with respect to learner factors (gender, origin, motivation), teaching context (course level, course duration, form of the assessment) and learning outcomes (course completion, perceived quality of instruction). The results of this study suggest that adopting a multi-dimensional, person-centred approach can be useful for researchers and practitioners to classify MOOC learners into subpopulations, design effective educational interventions that best engage different types of learners, and provide support and scaffolding to individuals with idiosyncratic or problematic engagement patterns.