Map - Eyüp (Eyüpsultan)

Eyüp or Eyüpsultan is a district of the city of Istanbul, Turkey. The district extends from the Golden Horn all the way to the shore of the Black Sea. Eyüp is also the name of a prominent neighborhood and former village in the district, located at the confluence of the Kâğıthane and Alibey streams at the head of the Golden Horn. The Eyüp neighborhood is a historically important area, especially for Turkey's Muslims, due to the presence of the tomb of Abu Ayyub al-Ansari.

It became a district centre in 1936, after some parts of Fatih, Çatalca and Sarıyer were joined; later it also included Gaziosmanpaşa and Bayrampaşa districts. Its present boundaries were established after the borough of Yayla was given to Sultangazi in 2009. Its neighbours are Sarıyer in the east, Kâğıthane and Beyoğlu in the southeast, Gaziosmanpaşa, Bayrampaşa, Fatih and Sultangazi in the south, Başakşehir in the southwest and Arnavutköy in the west, It was named after Abu Ayyub al-Ansari by the Ottoman Turks.

Modern Eyüp was the site of a settlement already in the Byzantine period, best known as Kosmidion (Κοσμίδιον). Its name derives from the local monastery of the Anargyroi (Saints Cosmas and Damian), which was established in the fifth century. According to a later legend, it was founded by the magister Paulinus, who was executed by Theodosius II (r. 408–450) when the latter suspected him—erroneously—of having an affair with empress Aelia Eudocia. In reality, however, the monastery was probably founded ca. 480 by Paulina, the mother of the general and failed usurper Leontius. From her, the quarter was initially known as ta Paoulines (τα Παυλίνης, "Paulina's [quarter]"). The monastery was of some importance in the sixth century: its abbots participated in synods of 518 and 536, a collection of miracles associated with its patron saints appeared, and the monastery received a major renovation as part of the building programme of Justinian I (r. 527–565). In 623 and again in 626, the site was besieged and looted by the Avars.

By the early tenth century, the quarter that grew around the monastery had become known as Kosmidion; alternatively, but less likely, Kosmidion and ta Paoulines may have been neighbouring but separate localities. In 924, Emperor Romanos I Lekapenos (r. 920–944) met with the Bulgarian Tsar Simeon at a pier in Kosmidion during the Byzantine–Bulgarian war of 913–927. Theophylact Lekapenos, Romanos' son and Patriarch of Constantinople in 933–956, had his stables there.

Emperor Michael IV (r. 1034–41) renovated the monastery complex anew, and retired there following his abdication. He died there as a monk soon after. Due to its proximity to Constantinople, the site played a role in the civil wars of the period: it was the headquarters of the rebel Leo Tornikios (although other sources place his headquarters at Thermopolis) during his failed siege of the imperial capital in 1047, it was a base of John Bryennios, brother of the rebel general Nikephoros Bryennios the Elder, in 1077, and four years later, it was one of the first localities taken over by the Komnenoi in their successful coup against Nikephoros III Botaneiates (r. 1078–81). In 1096, the newly arrived First Crusade was allowed to encamp between Kosmidion and Hagios Phokas.

During the Fourth Crusade, Kosmidion was the site of one of the first skirmishes between the Crusaders and the Byzantines in July 1203, from which the Crusaders emerged victorious. In April 1204, shortly before the fall of the city to the Crusaders, the Venetian Doge Enrico Dandolo met with the newly crowned emperor Alexios V Mourtzouphlos for negotiations there.

Under Latin rule, the monastery seems not to have suffered too much; certainly it was fit to lodge Emperor Michael VIII Palaiologos (r. 1259–82) on the night of 14 August 1261, before his triumphal entry into recently recovered Constantinople the next day. In the next decades, the monastery was used as a place of exile for two disgraced patriarchs, Joseph I in 1280–82 and John XI Bekkos in 1285, while awaiting trial by the synod, and Athanasius I for the period before his abdication in 1293. A collection of miracles attributed to the monastery's patron saints since 1261 was compiled in ca. 1300 by a certain deacon Maximos.

In 1303 Spanish mercenaries from the Crown of Aragon in imperial service took over and fortified the monastery complex as a base of operations against the Genoese colony of Galata. Following the breach between the Empire and the Catalan Company in 1305, however, the Byzantines evacuated the site. In the 1348 war with the Genoese, the latter captured and burned all Byzantine ships in the Golden Horn, except the three being built in a dockyard in Kosmidion. In 1350 the monastery was visited by the Russian pilgrim Stephen of Novgorod. At about the same time, the existence of a church dedicated to a St. Theodore, as well as a chapel dedicated to the martyrs Thalelaios and Artemidoros, is known, without further information.

In 1410, during the Ottoman Interregnum, the contenders for the Ottoman throne, Musa Çelebi and Süleyman Çelebi, clashed at Kosmidion, with the latter emerging as the victor.

After the Fall of Constantinople, the quarter was renamed after Abu Ayyub al-Ansari (Turkish: Eyüp), a companion (Ansari) of Muhammad who fell in the First Arab Siege of Constantinople in 674–678. In 1581, Christians were prohibited from living there.