An astronomical complex or commemorative astronomical complex is a series of man-made structures with an astronomical purposes. It has been used when referring to a group of Megalithic structures that it is claimed show high precision astronomical alignments. For the study of Archaeoastronomy, such complexes of similar structures are required for adequate measurement and calculation to ensure that similar celestial sightlines were intended by the designers. These arrangements have also been known as observational, ceremonial or ritual complexes with importance for the study of prehistoric cultures.
The term has been used in the naming of various series of observatories used for observing the stars in modern times.
Examples of suggested ancient astronomical complexes that may have been used as solar and lunar observatories include, in reverse-chronological order:
Examples of modern astronomical complexes of stellar observatories include: