The Haseki Hürrem Sultan Mosque, located in Fatih, Istanbul, serves as the centerpiece of the Haseki Complex and stands as an early exemplar of Ottoman classical architecture.

It marks the first significant work completed by Mimar Sinan after his appointment as chief imperial architect.

Commissioned in the 16th century by Hürrem Sultan, wife of Sultan Suleiman the Magnificent, the mosque was originally constructed between 1538 and 1539 as a single-domed structure. In 1612, it was expanded by chief architect Sedefkar Mehmed Ağa, who added a second dome, giving the mosque its current form.

The building was designed not only as a place of worship but also as the central component of a large complex (külliye). The külliye included a madrasa, a hospital, a soup kitchen, a primary school, and a bathhouse.

In Ottoman social life, the complex played an important role, particularly through its hospital and soup kitchen, contributing significantly to charitable institutions in Istanbul.

Architecturally, the mosque is considered an early example of Ottoman classical mosque architecture. Constructed with cut stone, its interior features a simple and balanced design.

Today, the Haseki Hürrem Sultan Mosque is recognized as one of Istanbul’s significant cultural assets, exemplifying the külliye tradition that combined religious, educational, and social welfare functions.

Dr. Resul Yelen, a faculty member at Istanbul Medeniyet University’s Department of Turkish and Islamic Art, explained that construction of the Haseki Sultan Complex began in 1538 with the mosque.

He explained that the mosque was built for Hürrem Sultan, and that Haseki Street was divided into two sections alongside the complex.

"This is Mimar Sinan’s first work after becoming the chief imperial architect. On the north side is the mosque, to the south are the imaret, primary school, hospital, and a fountain. According to inscriptions on the mosque, construction began in 1538 and was completed within a year. The other structures were completed 12 years later,” Yelen said.

He noted that the mosque was initially built with a square plan and a single dome, adding, "In 1612, due to the growth of the congregation, the mosque was expanded eastward by Sedefkar Mehmed Ağa, who was also a student of Mimar Sinan, thus extending his teacher’s work.”

With the expansion, the eastern wall was removed, and a square, single-domed section supported by two columns was added. The mihrab was relocated to the center to restore symmetry.

Yelen added that the mosque’s interior was divided into 2 domed spaces with 2 columns, featuring shell-shaped (tromp) transitions for the domes. The walls combine stone and brick, and the portico features diamond-patterned column capitals forming a five-unit entrance.

Although many interior decorations have been restored over time, the mosque retains its original stylistic features. The mihrab, placed centrally, features intricate calligraphic decoration, including vase motifs, relief designs, and a lamp motif in the niche, likely added during the Westernization period.

The area where the külliye was built has been referred to as Haseki since the 19th century. Yelen explained that when the complex and mosque were built, the district was known as Avrat Pazarı, or "Women’s Bazaar,” a name documented by Evliya Çelebi. He added that the mosque was constructed as a gesture by Sultan Suleiman for Hürrem Sultan.

The stone entrance of the mosque is richly decorated with shell-shaped and muqarnas details, with the shell motif repeated in both the dome transitions and the doorway. 2 inscriptions flank the gate, the right inscription features the phrase of monotheism (Kelime-i Tevhid), and the left inscription repeats the Prophet Muhammad’s name 4 times, written in a style known as makili.

Yelen also noted that Haseki Sultan commissioned charitable structures not only in Istanbul and Anatolia but also in Jerusalem, where one of her soup kitchens continues to operate today.

He emphasized that a powerful and influential female sultan continued the Ottoman tradition of charitable architecture across the territories under her influence.