Borromean rings

Borromean rings are three simple closed curves in three-dimensional space that are topologically linked and cannot be separated from each other, but that break apart into two unknotted and unlinked loops when any one of the three is cut or removed. [1]

There are two versions, a “fixed” and a “loose”. The fixed one fit perfectly and don't move after printing, whereas the loose ones move around. Both need to be printed with supports (organic/tree supports work best).

https://en.wikipedia.org/wiki/Borromean_rings