Khalid Muhammad Abdallah al-Mihdhar (Arabic: خالد المحضار‎‎, Khālid al-Miḥḍār; also transliterated as Almihdhar) (May 16, 1975 – September 11, 2001) was one of five hijackers of American Airlines Flight 77, which was flown into the Pentagon as part of the September 11 attacks. Khalid al-Mihdhar was born in Saudi Arabia and fought in the Bosnian War during the 1990s. In early 1999, he traveled to Afghanistan where, as an experienced and respected jihadist, he was selected by Osama bin Laden to participate in the attacks. Mihdhar arrived in California with fellow hijacker Nawaf al-Hazmi in January 2000, after traveling to Malaysia for the Kuala Lumpur al-Qaeda Summit. At this point, the CIA was aware of Mihdhar, and he was photographed in Malaysia with another al-Qaeda member who was involved in the USS Cole bombing. The CIA did not inform the FBI when it learned that Mihdhar and Hazmi had entered the United States, and Mihdhar was not placed on any watchlists until late August 2001.

Upon arriving in San Diego, California, Khalid al-Mihdhar and Hazmi were to train as pilots, but spoke English poorly and did not do well with flight lessons. In June 2000, Mihdhar left the United States for Yemen, leaving Hazmi behind in San Diego. Mihdhar spent some time in Afghanistan in early 2001 and returned to the United States in early July 2001. He stayed in New Jersey in July and August, before arriving in the Washington, D.C. area at the beginning of September. On the morning of September 11, 2001, Khalid al-Mihdhar boarded American Airlines Flight 77, which was hijacked approximately 30 minutes after take off. The plane was deliberately crashed into the Pentagon, killing all 64 people aboard the flight, along with 125 on the ground.