A reinforcement structure for a vacuum interrupter is disclosed. For example, in some implementations, a vacuum interrupter includes a first electrical contact; a second electrical contact; a vessel that encloses the first electrical contact and the second electrical contact in an evacuated space, the vessel including an endcap; and a reinforcement structure at an exterior surface of the endcap, the reinforcement structure including a first side, a second side, and an opening that passes through the reinforcement structure from the first side to the second side. The exterior surface of the endcap includes a recessed region, and at least a portion of the opening is positioned over the recessed region.