The Michael Carlos Museum at Emory University in Atlanta, which bought the mummy three years ago from a museum in Ontario, returned the relic after determining it may be the founder of the 19th Dynasty and grandfather of Ramses II.
"Welcome Ramses, the builder of esteemed Egypt," a children's chorus sang as the box containing the mummy was brought into the Egyptian Museum.
Zahi Hawas, head of Egypt's Supreme Council of Antiquities, said it wasn't certain that the mummy is Ramses I, but the return was "a great, civilized gesture" by the museum.
"We are not 100 percent sure that the mummy is that of Ramses I, but we are 100 percent sure that it is of a king," Hawas said.
The mummy was taken, he said, along with other artifacts from the tomb of Ramses I in Egypt's Valley of Kings.
Other experts, including Emily Teeter, curator of Egyptian antiquities at the University of Chicago's Oriental Institute, have said there is no hard evidence that the returned mummy is Ramses. Without a DNA match, scholars have relied on historical, archaeological and other scientific evidence to identify the mummy.
Many cite the position of the mummy's arms: crossed high over his chest in a fashion reserved for royal mummies at the time of Ramses' death. Some say he bears an undeniable resemblance to the pharaohs Seti I and Ramses II, descendants whose mummies have been identified.
Hawass ruled out the possibility of DNA tests, calling them unreliable. Egyptian antiquity officials have always rejected DNA tests on mummies of pharaohs, possibly fearing the tests could challenge established theories.
Hawass said the mummy will be displayed next year at the Luxor Museum in southern Egypt.
He appealed to other world museums to return Egypt's antiquities and masterpieces, particularly the bust of Nefertiti, in the Berlin Museum, and the Rosetta Stone, which is in the British Museum.
The mummy returned Sunday was the centerpiece of a large Egyptian collection the Emory museum purchased in 1999 from the Niagara Falls Museum in Ontario, Canada.
The Ontario museum likely received the mummy from a Canadian doctor who had the artifacts smuggled out of Egypt in the early 1860s.
Ramses I, ancestor of Egypt's most illustrious rulers, ruled for only two years, from from 1292-1290 B.C. He was the first of 11 rulers by the name Ramses in the 19th Dynasty.
By Salah Nasrawi