There was a real man named Imhotep in ancient Egypt, but he and his cinematic counterpart have little in common, except for a great devotion to the women they loved.

The name means "The one who comes in peace."  (Definitely not applicable to the movie's Imhotep!)

While the  cinematic Imhotep was the High Priest of Osiris (and had some run-ins with Anubis), the real Imhotep was associated with Ra, Ptah, and Thoth.  (One source I found said he was a priest of Ra, but another said he was a priest of Ptah and was later called the son of Ptah.  Thousands of years after his death, he was worshipped as a god of knowledge and linked to Thoth.)

The real Imhotep was born a commoner but achieved great power and respect due to his brilliance.  He lived in the Old Kingdom period, during the 3rd Dynasty  (approx. 2650 BC).

Imhotep served as vizier to Pharaoh, as well as a head architect, priest,  astrologist,  doctor,  and sculptor.   His plan for irrigation, food preservation and fishieries management ended a seven-year famine in Egypt.

One legend says that after  word of Imhotep's great medical knowledge spread, he was called to the court of Pharaoh Khasekhem.  He soon saved the life of  Pharaoh's Great Royal Wife, who had a very difficult time giving birth to Prince Djoser.  Tragically, at the same time as Imhotep was battling to save the Queen's life, his own wife was in labor with their son, and died.  Their son was put under the care of the Queen's nurse while Imhotep locked himself in with his wife's body through the 40 days of  mummification and burial preparation.

Imhotep buried his beloved wife in the desert near Saqqara, and legend has it that he swore someday to return and raise a great building over her grave, which he did  when he was responsible for the construction of Egypt's very first stone pyramid.  

The pyramid was constructed of small stone blocks instead of the traditional mud bricks, and soared 200 feet in the air.   It was built as the tomb of Pharaoh Djoser, but Imhotep was probably buried in the Step Pyramid complex, as well,  although no site has thus far been conclusively proven to be his tomb.

Imhotep was actually more respected and famed as a physician than as an architect.  Some even believe him to be true father of modern medicine, even before Hippocrates.  (Somehow I don't imagine young doctors swearing the Imhotepian Oath any time soon, however!)

 Imhotep's deeds made him a very well respected man, and after his death he was among the first and few non-royals to be posthumously deified in Egypt.   By the reign of Amenophis III in the New Kingdom era, Imhotep was honored as a demi-god and offered water oblations.  The Greeks associated him with their healing god, Asklepios.   King Hadrian later favored him as well, and the Romans built an obelisk monument to him, reading, "He hears the plea of him who calls him.   He lets the needy become well."   Evidence indicates that he was worshiped at the Step Pyramid complex in Ptolemaic times. 

Imhotep's achievements seemed so extrordinary that some Egyptologists even doubted that he was a real person until his name was found inscribed on the base of a statue in the enclosure of the Step Pyramid.

Below is a statue found at Saqqara that may depict the real Imhotep.  (Less scary than Boris Karloff, but not as handsome as Arnold Vosloo! )

Here's another statue said to depict Imhotep.