Islam-aga's Mosque, Ottoman mosque in Niš, Serbia

Islam-aga's Mosque is a rectangular Ottoman building with a flat wooden ceiling and a gallery, founded in 1870 on the foundations of an older mosque from 1720. It has no major architectural value and stands on General Miloje Lešjanin Street in central Niš.

A damaged Ottoman mosque from 1720 stood here before the wealthy Niš resident Islam-aga Hadrović Đakovalija built the present mosque on its foundations in 1870, shortly before Niš was liberated from Ottoman rule. Of the nineteen mosques that existed in Niš under Ottoman rule, this is the only one preserved and fit for religious use. It was protected by the state in 1954, damaged by stone-throwing in 2003 and by arson in 2004, and fully renovated by the end of August 2013.

The mosque is used by the Mejlis of the Islamic Community of Niš, the only congregation still worshipping in a mosque in the city; the town has also planned to restore the Hasan-beg Mosque in Šumatovačka Street for use. It is listed as a Monument of Culture of Great Importance, cared for by the Niš Institute for the Protection of Cultural Monuments.

The mosque stands on Ulica Generala Milojka Lešjanina in central Niš, outside the old fortress walls. It is the only mosque in the city still used for worship, so time a visit outside prayer hours and dress modestly. The building has a rectangular plan with a flat wooden ceiling and a gallery.

The mosque was stoned on the night of 27–28 August 2003, when about a hundred Partizan fans celebrating the club's Champions League qualification broke two windows. It was then set on fire on 17 March 2004, in retaliation for the destruction of churches and monasteries in Kosovo and Metohija.