Using a Green's function method, we study the magnetoresistance (MR) effect in a ring-shaped array of magnetic quantum dots (QDs), with or without magnetic leads, while the magnetic QDs play the role of magnetic layers in conventional multilayer MR devices. Due to the multiple electronic interferences in this proposed ring-shaped structure, it exhibits extremely large MR values, typically up to four million percent (3.9 × 106% in an array that includes 14 QDs), as it tends to be infinite for a system with more dots. Our results show that when the magnetic moment of all QDs is parallel (antiparallel), the charge current through the outgoing lead is maximal (minimal). In addition, the Rashba spin-orbit interaction and the bias voltage are two significant factors that can control the MR values. Besides, by adjusting the magnitude of the magnetic moment of the QDs, the MR effect can be optimized. Finally, it is revealed that the onsite energy of the QDs is an effective parameter for modifying the value and sign of the MR percentage. Consequently, this ring-shaped structure, with controllable parameters and impressive MR percentages, can be an efficient preferred alternative for ordinary layered MR-based devices, for design of the next generation of nanoscale spintronic systems.