either of two temples of ancient Egypt, dedicated to the worship of the Greco-Egyptian god Serapis (Sarapis). The original elaborate temple of that name was located on the west bank of the Nile (Nile River) near Ṣaqqārah and originated as a monument to the deceased Apis bulls, sacred animals of the god Ptah. Though the area was used as a cemetery for the bulls as early as 1400 BC, it was Ramses II (1279–13 BC) who designed a main gallery and subsidiary chambers (repeatedly enlarged by succeeding kings) to serve as a catacomb for the deceased Apis bulls who, in death, became assimilated to the god Osiris as Osiris-Apis. The Greeks living near Ṣaqqārah worshiped this god as Osorapis, which under the Ptolemaic dynasty became Serapis, and the temple was thereafter called the Serapeum.

The ruins of the Serapeum at Ṣaqqārah were first discovered in 1850 by Auguste Mariette (Mariette, Auguste), a French Egyptologist. The subterranean chambers, which he entered in 1851, yielded the burials of 64 Apis bulls, together with thousands of inscribed objects. A second area of the Serapeum underwent excavation beginning in the 1980s.

Another important Serapeum was built at Alexandria, the new Ptolemaic capital. When Ptolemy I Soter (reigned 305–284 BC) wanted to select an official god for Egypt, he chose Serapis, ordering his architect Parmeniscus to design what became one of the largest and best known of the god's temples. There Serapis was worshiped in a purely Greek ritual until AD 391, when the Serapeum was destroyed by the patriarch Theophilus (Theophilus of Alexandria, Saint) and his followers. In Roman times other Serapeums were constructed throughout the empire.