Maguire had intended to join a delegation of women activists going to the blockaded Palestinian enclave tomorrow.
The group could embarrass Egypt's military-installed government, which is at odds with Gaza's militant Hamas rulers, yet does not want to be seen as party to a siege of Palestinians.
Airport police yesterday detained and deported American anti-war activist Medea Benjamin, also part of the delegation. She told AFP her arm was broken by the policemen.
"We were taken to the detention centre and questioned and held for eight hours, and were told we would not be allowed entry into Cairo and would be put on a plane," she told AFP by telephone from Britain.
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She said the police were "polite" but offered her no reason for barring her, but an airport official told AFP she had been blacklisted.
Maguire, born in 1944, won the 1976 Nobel Peace Prize with Betty Williams for founding a peace group to resolve the conflict in Northern Ireland.
The delegation of activists that will try to enter Gaza through the Egyptian Rafah border crossing is led by Djamila Bouhired, an icon of the Algerian war of independence from France.
She is due to arrive at Cairo airport at 1800 GMT aboard a flight from Paris, and it was not immediately clear whether she would be allowed into the country.
Egypt controls the only border crossing with Gaza that bypasses Israel, and is accused of colluding with Israel to blockade the territory ruled by the militant Islamist group Hamas.