In this article, a novel isolated circuit breaker (ISCB) that realizes robust interruption capability is proposed for direct current microgird protection. First, the proposed ISCB isolates the main current path and the commutating circuit during the fault-clearing state, thereby not causing fault current surges on both the input and output sides, and effectively protecting the source and load. Second, the ISCB can automatically charge the commutating capacitor to offer interruption capability before the reclosing of the breaker, which ensures a safe restart of microgrids after faults (especially temporary faults). Third, due to the introduced voltage clamping circuits, the ISCB can successfully interrupt faults without being effected by parasitic parameters on microgrids. Finally, the use of the insulated gate triggered thyristor with strong tolerance to current and voltage surges can also enhance the robustness of the ISCB. Consequently, the ISCB features higher fault interruption robustness than the existing breakers. Moreover, design guidelines are provided through mathematical modeling, and then based on the design guidelines, a laboratory prototype is developed to validate the feasibility of the ISCB.