Seyyed Alauddin Hossein (Persian: سید علاء الدین حسین; c.1592 – 5 March 1654), better known as Khalifeh Soltan (خلیفه سلطان), and also known as Soltan al-Ulama (سلطان‌العلماء آملی), was an Iranian statesman and cleric, who served as the grand vizier of the Safavid king (shah) Abbas I (r. 1588–1629), the latter's grandson Safi (r. 1629–1642), and Abbas II (r. 1642–1666).

A member of a prominent Seyyed family with origins in the royal Marashi family of Mazandaran, Khalifeh Soltan was a well-educated man of letters, who played an important role in the Iranian clergy affairs, and also later in the Safavid administration, when he was appointed as grand vizier in 1623/4.

He was, however, in 1632, disgraced and exiled by the ruthless newly crowned shah Safi. Later, in 1645, Khalifeh Soltan was re-appointed as grand vizier by the latter's son and successor, Abbas II, whom he became a close companion of, and gained considerable influence. Khalifeh Soltan later died on 5 March 1654 in his ancestral homeland of Mazandaran due to illness, and was succeeded by Mohammad Beg.

Khalifeh Soltan's full name was Seyyed Alauddin Hossein Hosseini Marashi Amoli Isfahani; he was born in ca. 1592/93 in Isfahan, where he grew up; his father Mirza Rafi al-Din Muhammad was a prominent aristocrat who occupied high offices in the Safavid Empire, and belonged to a family known as the "Shahristani sayyids", which was descended from Shah Nimatullah, the founder of the Nimatullahi order. Khalifeh Soltan's mother belonged to a family known as the "Khalifeh sayyids", a family of Marashi descent, whose ancestor, Amir Nezam al-Din, was forced to settle in the Golbar quarter of Isfahan in the 15th century. Khalifeh Soltan was thus related to Shah Abbas I, whose mother was Khayr al-Nisa Begum, a Marashi princess who had fled to the Safavid court and married the previous Safavid shah Mohammad Khodabanda (r. 1578–1587).

Even though the Khalifeh seyyed family was renowned of being descendants of the celebrated Marashi ruler Mir-i Buzurg (r. 1359–1362), they still weren't one of the leading families of Isfahan yet. But they were still affluent and distinguished enough to intermarry with local well-known families. According to the Safavid court historian Iskandar Munshi, "The Khalifeh family had held estates in the Isfahan area for generations."

Khalifeh Soltan had a brother named Mirza Qavam al-Din Mohammad, who later, like himself and their father, would occupy high offices.

On 28 November 1607, Khalifeh Soltan married shah Abbas I's third daughter, Khan-Agha Begum. After the marriage, Khalifeh Soltan asked for the governorship of Tabriz as an outcome of the cheerful circumstance, which was, however, declined. This demonstrates Khalifeh Soltan's early passion in getting a role in the state bureaucracy.

Khalifeh Soltan was later in 1623/4 appointed by the shah as his grand vizier. When Khalifeh Soltan became grand vizier, Baghdad had recently been captured, while a Safavid army was marching towards Basra to capture it. Furthermore, during this period, the Armenians suffered from persecutions by Abbas I. In late 1624, after celebrating Nowruz, Abbas I left for Georgia to suppress a rebellion, thus leaving the young Khalifeh Soltan in Isfahan, to take care of the Safavid affairs.