<p>The bending behaviour of rectangular cantilevered thin plates remains one of the most challenging classical problems in plate theory, mainly due to the mathematical intricacies associated with two types of corner regions: the junctions between clamped and free edges, and the intersections of two free edges. Traditional series expansion methods often fail to produce truly convergent or physically meaningful solutions—especially along the plate boundaries—due to inadequate treatment of two types of corner regions. This paper extends the previously proposed novel and robust series expansion method to the cantilever plate problem and systematically addresses these challenges. By applying particular closed-form solutions and carefully tailoring the functional form of each series expansion to the corner properties, the proposed method ensures both mathematical convergence and physical realism. In particular, the analytical solutions obtained here represent, in the strictest sense, the first truly accurate and convergent solutions for cantilever plates subjected to uniformly distributed loads. The approach provides significantly faster convergence, higher computational efficiency and greater accuracy compared to traditional techniques. Furthermore, the results not only validate and extend existing findings, but also expose fundamental flaws in several previously claimed “exact” solutions. This work sets new benchmarks for analytical accuracy in the study of cantilevered plate structures.</p>