The university said the decision was mutual. "Professor Ramadan's teaching, supervising and examining duties will be reassigned," it said in a statement, "and he will not be present at the University or College."
The statement added: "The University has consistently acknowledged the gravity of the allegations against Professor Ramadan, while emphasizing the importance of fairness and the principles of justice and due process," the statement added.
Mr. Ramadan, 55, a Swiss-born theologian and philosopher, is a professor of contemporary Islamic studies at the university and a senior research fellow at St. Antony's, an Oxford college that focuses on international affairs.
The accusations have created a storm in Islamic and academic circles across Europe. Mr. Ramadan is a grandson of Hassan al-Banna, who founded the Muslim Brotherhood in Egypt in the 1920s. He is the author of a dozen books in English on modern Islam and the Western world, and a familiar presence on television news shows and on social media.
Mr. Ramadan has said that the accusations are unfounded and has vowed to fight the cases in court. He has filed a defamation suit in Paris against one of his accusers, the French activist and author Henda Ayari.
Ms. Ayari accused Mr. Ramadan of raping and assaulting her in a hotel on the sidelines of a conference in Paris in 2012. She said Mr. Ramadan had acted as an online teacher and mentor to her and then had suggested one day that they meet at his hotel.
She wrote about the encounter in a book in 2016, but did not name her attacker at the time. Last month, encouraged by the wave of denunciations by women outing their sexual aggressors in the #MeToo campaign on social media after the Harvey Weinstein scandal, Ms. Ayari identified Mr. Ramadan as her attacker. She said she had not spoken out earlier because Mr. Ramadan had threatened her and her children.
Ms. Ayari has lodged a complaint with French police, alleging rape, sexual assault, harassment and intimidation. Her lawyers said she had also submitted evidence with her complaint.
A second Frenchwoman has also filed a complaint with police in Paris, accusing Mr. Ramadan of assaulting and raping her in a hotel in Lyon in 2009. That woman, who has not been named publicly, described a horrifying assault by Mr. Ramadan to two French newspapers.
Other allegations have surfaced in French and Swiss newspapers, including accounts from two women who said they had sexual relations with Mr. Ramadan before they had reached the age of consent, and a third who described having a consensual but violent relationship with him.
In a statement on his Facebook page on Tuesday, Mr. Ramadan saluted the position taken by Oxford. The leave of absence, he said, "will permit me to devote my energies to my defense while respecting students' need for a calm academic environment."
Mr. Ramadan said in an earlier Facebook post that the allegations were the work of his enemies and said he was preparing for a prolonged legal battle. His supporters have hurled insults and threats at Ms. Ayari on social media, accusing her of seeking publicity for her book or even of pursuing a Zionist plot against Mr. Ramadan.
Students at Oxford's Faculty of Oriental Studies, where Mr. Ramadan teaches, had complained about the university's slow response to the allegations, according to Cherwell, a student newspaper.
Members of the faculty at first said they expected Mr. Ramadan to continue teaching and supervising students last week, but complaints from students grew, the newspaper reported.
Mr. Ramadan's leave of absence "implies no presumption or acceptance of guilt and allows Professor Ramadan to address the extremely serious allegations made against him," Oxford's statement said, "while meeting our principal concern — addressing heightened and understandable distress, and putting first the well-being of our students and staff."
Asked about students' complaints, Eugene Rogan, director of the Middle East Center at St. Anthony's, emphasized that student security was a paramount concern.
"It is important to note that since the reported meeting Tariq Ramadan has not taught at Oxford and, in fact, has not been in the city," he said in a statement. "Nevertheless, my colleagues and I contacted each of Professor Ramadan's students, and made alternative teaching arrangements for any student who asked for them."