Katib al-Wilaya Mosque or Welayat Mosque (Arabic: جامع الولايات) is a small historic mosque located along Omar Mukhtar Street in Gaza City in the Zaytun Quarter of the Old City. The mosque was built by the Burji Mamluks in 1432, however, the structure could date further back to 1344. Additions to the western part of the mosque were commissioned in 1584 by Ahmed Bey, the Ottoman clerk of the Damascus Vilayet (Province of Damascus). Damascus Vilayet's Arabic transliteration is Wilayat Dimashq, hence the name of the mosque Katib al-Wilaya ("the clerk of the state").
The minaret of the mosque, rising above the mosque's eastern wall, is adjacent to the bell tower of the St. Porphyrius Church. Palestinian historian Aref al-Aref says local legend attributes this positioning of the building to the Rashidun caliph Umar ibn al-Khattab's orders to the Muslim general Amr ibn al-'As to build a mosque next to every church in the lands conquered by the Muslims. Another anecdote claims the mosque had earlier been a monastery known as Deir Salm al-Fada'il. Both of these accounts lack any verifiable basis other than local folklore.