The characters of Bernard Lewis's The Crisis of Islam are historical figures, as his account is a nonfiction history of Islam and the Middle East. The book is largely dedicated to explaining the history of the religion whose extremists ultimately led to the the 9/11 terrorist attacks.

The first principal character is Muhammad, the founder of Islam. Islam holds that Muhammad, born at the end of the sixth century CE, is God's prophet. The historical Muhammad was born in Mecca, where he faced persecution which led him to lead his group of followers to Medina. Muhammad's father-in-law, Abu Bakr, became his first successor. He was called kalifa (alternatively "successor" or "deputy"), a term which gave its name to the institution of the caliphate. When Muhammad died in 632 CE, he was understood as having fulfilled the prophecy of bringing God's word to the people.

Ayatollah Khomeni is another historical figure discussed by Lewis. Khomeni was the leader of the 1979 Iranian Revolution, in which the monarch of Iran was overthrown. This was a watershed moment in Islam, according to Lewis, as it represented a victory of Muslims (in their view) over the infidels. Khomeni spent the latter part of his life in exile in Iraq, and he was famous for introducing sharia (Islamic law). Khomeni issued a fatwa against novelist Salman Rushdie for Rushdie's publication of The Satanic Verses.

Two other prominent characters in Muslim history addressed by Lewis are Saddam Hussein and Osama bin Laden. Hussein was president of Iraq and leader of the Arab world, and he developed a personality cult surrounding himself. After the US won the Gulf War, Hussein grew increasingly antagonistic to the United States. He led brutal attacks on Iran and was eventually captured by US soldiers.

Finally, Lewis outlines the rhetoric and tactics of military leader Osama bin Laden. Bin Laden used Qur'anic rhetoric to garner support for his regime. He likened President Bush to the biblical Pharaoh and was extremely offended by non-Muslim presence in the Middle East.