Q: Is there a mosque inside the Pentagon?
A: The Pentagon has a non-denominational chapel that holds services for employees who follow various religions.
FULL QUESTION
I’ve read in various articles about there being an actual Muslim mosque in the Pentagon itself. However, there are some people that deny it even exists. I can’t seem to find a definite answer anywhere online about this subject. Can anyone at FactCheck.org shed any light on whether this is true or false?
FULL ANSWER
On CNN’s "State of the Union" on Aug. 15, Democratic Rep. Jerrold Nadler of New York spoke in favor of a Muslim group’s right to build a controversial Islamic center and mosque near ground zero in New York. Nadler pointed out to host Candy Crowley that no one had similarly objected to "a mosque in the Pentagon, which is also hallowed ground."
Salon.com’s Justin Elliott also pointed out in a blog item titled "Why did no one object to the ‘Pentagon mosque’?" that Muslims have been holding prayer services in the Pentagon for several years. 
The truth is that there is no "mosque" in the Pentagon, according to Army spokesman George Wright. There is a chapel inside the Pentagon where Muslim employees can go to pray, as ABC News recently reported. It’s just not exclusive to followers of Islam.
The Pentagon’s non-denominational chapel was built and dedicated in 2002 in honor of Pentagon employees and passengers of American Airlines Flight 77 who died in the terrorist attack on the building on Sept. 11, 2001. The chapel was constructed at the site where the hijacked plane crashed into the Pentagon nearly nine years ago.
Wright told us that the chapel, which can seat about 100 people, hosts services throughout the week for Pentagon employees of various faiths including Catholics, Protestants, Jews, Episcopalians, Hindus and Muslims. Wright said that the chapel’s schedule for the week of August 16 actually includes daily mass for Catholics; Bible study sessions for Protestants, Jews and members of the Church of Jesus Christ of Latter-day Saints; as well as a prayer service for Muslims.
The chapel is run by the Office of the Pentagon Chaplain, and prior to its construction, all religious services were reportedly held in either conference rooms, auditoriums or informal prayer rooms inside the Pentagon.
–D’Angelo Gore
Correction, Aug. 26: We originally used an abbreviated and incorrect name for the Church of Jesus Christ of Latter-day Saints. We have corrected the error.
Sources
Wright, George, Army spokesman. Interview with FactCheck.org. 17 Aug 2010.
Martinez, Luis. "Mosque Controversy Skips Pentagon: Muslims Gather in Daily Prayer at 9/11 Crash Site." ABC News. 17 Aug 2010.
Orme, Nate. "Pentagon opens 9-11 Memorial Chapel." MilitaryInfo.com. 18 Sep 2002.
Rhem, Kathleen T. "Military Clergymen Dedicate Pentagon Memorial Chapel." Armed Forces News Service via defense.gov. 12 Nov 2002.