在天文学里，空洞指的是纤维状结构之间的空间，空洞与纤维状结构一起是宇宙组成中最大尺度的结构。空洞中只包含很少或完全不包含任何星系。

一个典型的空洞直径大约为11至150个百万秒差距；特别的，对于空间等同超星系团的大型空洞，时常被称为超级空洞或超空洞。

1994年的一次宇宙观测列出了地球附近740个百万秒差距内的全部27个超级空洞；以下列出全部：

Cosmic voids are the vast empty spaces between filaments (the largest-scale structures in the Universe), which contain very few, or no, galaxies. Voids typically have a diameter of 10 to 100 megaparsecs; particularly large voids, defined by the absence of rich superclusters, are sometimes called supervoids. These zones have less than one-tenth of the average density of matter abundance that is considered typical for the observable Universe. They were first discovered in 1978 during a pioneering study by Stephen Gregory and Laird A. Thompson at the Kitt Peak National Observatory.