The Ramesseum is the memorial temple (or mortuary temple) of Pharaoh Ramesses II ("Ramesses the Great"). It is located in the Theban Necropolis in Upper Egypt, on the west of the River Nile, across from the modern city of Luxor.

It is the second largest temple in Egypt, occupying an area of c. 10 hectares (1,100,000 sq ft).

It was originally called the House of millions of years of Usermaatra-setepenra that unites with Thebes-the-city in the domain of Amun. Usermaatra-setepenra was the prenomen of Ramesses II.

Ramesses II modified, usurped, or constructed many buildings from the ground up, and the most splendid of these, in accordance with New Kingdom royal burial practices, would have been his memorial temple: a place of worship dedicated to pharaoh, god on earth, where his memory would have been kept alive after his death. Surviving records indicate that work on the project began shortly after the start of his reign and continued for 20 years.

The design of Ramesses's mortuary temple adheres to the standard canons of New Kingdom temple architecture. Oriented northwest and southeast, the temple itself comprised two stone pylons (gateways, some 60 metres (200 ft) wide), one after the other, each leading into a courtyard. Beyond the second courtyard, at the centre of the complex, was a covered 48-column hypostyle hall, surrounding the inner sanctuary. An enormous pylon stood before the first court, with the royal palace at the left and the gigantic statue of the king looming up at the back. As was customary, the pylons and outer walls were decorated with scenes commemorating the pharaoh's military victories and leaving due record of his dedication to, and kinship with, the gods. In Ramesses's case, much importance is placed on the Battle of Kadesh (ca. 1274 BC); more intriguingly, however, one block atop the first pylon records his pillaging, in the eighth year of his reign, a city called "Shalem", which may or may not have been Jerusalem. The scenes of the great pharaoh and his army triumphing over the Hittite forces fleeing before Kadesh, as portrayed in the canons of the "epic poem of Pentaur", can still be seen on the pylon.

Unlike the massive stone temples that Ramesses ordered carved from the face of the Nubian mountains at Abu Simbel, the inexorable passage of three millennia was not kind to his "temple of a million years" at Thebes. This was mostly due to its location on the very edge of the Nile floodplain, with the annual inundation gradually undermining the foundations of this temple and its neighbours. Neglect and the arrival of new faiths also took their toll: for example, in the early years of the Christian Era, the temple was put into service as a Christian church.

This is all standard fare for a temple of its kind built at that time. Leaving aside the escalation of scale – whereby each successive New Kingdom pharaoh strove to outdo his predecessors in volume and scope – the Ramesseum is largely cast in the same mould as the ruined temple of Amenhotep III that stood behind the "Colossi of Memnon" a kilometre or so away, and Ramesses III's Medinet Habu which closely followed the plan of the Ramesseum. Instead, the significance that the Ramesseum enjoys today owes more to the time and manner of its rediscovery by Europeans.

The Ramesseum was entered through a Pylon which led to the first courtyard. At its rear stood a pair of colossal statues, which flanked the second pylon. The larger of the two was called "Sun of the princes" and represented Ramesses, the smaller one his mother Tuya.