During recent decades, the versatile chemistry of crown-ethers and their complexes has generated interest in related macrocycles of heavier chalcogen elements.^1,2  Several reviews have been published in recent years since 2000 describing the progress in synthetic methods for the preparation, structural characterization, and coordination chemistry of heterocyclic chalcogenoethers, which is largely due to contributions by Levason and Reid, by Pinto, and by Gleiter, and their co-workers.^3–16  Research literature describing progress in heterocyclic chalcogenoethers is very extensive concentrating mainly on thioethers, and a complete review is beyond the scope of this chapter. This discussion is restricted to macrocyclic seleno- and telluroethers of ring size above ten and containing unbranched aliphatic spacers. The study of macrocyclic chalcogen heterocycles helps to gain insight on the chalcogen bonding and its application in supramolecular chemistry and crystal engineering.^17–22  This chapter is therefore concerned not only with syntheses and molecular structures, but also with bonding, and solid-state intermolecular interactions of saturated selenoether and telluroether macrocycles.