The blast in the Harthiyah area, which also wounded at least 30 people, is the latest in a string of bombings in the Iraqi capital that have killed dozens of people in recent days.
There was no immediate claim for the attack, but suicide bombings are almost exclusively carried out by Sunni jihadists in Iraq, including members of the Islamic State (IS) group, which has seized large areas of Iraq since June.
The militants have been kept from reaching Baghdad in force and would face major challenges if they tried to occupy part of the city, but they are able to strike the capital with deadly bombings.