Manganese dioxide (MnO2) has been considered one of the most attractive materials for the oxygen evolution reaction (OER) due to its low cost, natural abundance, easy synthesis, multiple morphology and polymorph, environmental friendliness, and high potential theoretical catalytic performance. However, the unsatisfactory oxygen evolution reaction (OER) efficiency of MnO2-based materials has confined their practical applications. Fortunately, recently, enormous efforts have been invested to improve the oxygen evolution reaction efficiency and clarify underlying mechanisms. Here, the aim is to exhaustively summarize the recent advances in the application of manganese dioxide and its composites as electrocatalysts for the oxygen evolution reaction. Fundamentally, the mechanisms and correlatively critical parameters of OER catalysis are discussed. Moreover, the diverse preparation routes of MnO2 nanomaterials are itemized elaborately. The morphology control, structure construction, facet engineering, element doping, and construction of binary/ternary heterojunctions are presented. Their applications in OER catalysis are also highlighted. Finally, a proposal for the research gaps and perspective on the challenges and development direction for future research on nanostructured MnO2-based materials in the field of OER catalysis applications has been propounded. Therefore, this review provides basic guidance for the rational design and construction of high-efficiency MnO2-based catalysts for OER.