Linked from
The 21 pages that link to Jordan curve theorem, each with the reason it gives.
Camille JordanBroader topic: Jordan proved this foundational result in topology.
Closed curveRelated: It states the key separation property of simple planar loops.
Pick's theoremRelated: Its notion of an enclosed interior underlies the theorem's count I.
Erdős–Nagy theoremRelated: A simple polygon has a well-defined bounded interior to convexify.