Ghiyath al-Din (Arabic: غیاث الدین), also transcribed as Ghiyāthu'd-Dīn, Ghiyasuddin, etc. is the name of many persons in the Islamic world. It may refer to:

• Ghiyath ad-Din Muhammad Tapar (died 1118), Seljuk Sultan
• Ghiyath al-Din Abu'l-Fath Umar ibn Ibrahim Al-Nishapuri al-Khayyami, better known as Omar Khayyam, (1048–1131), Persian scientist and poet
• Ghiyasuddin Iwaz Shah (1150–1227), ruler of Bengal
• Ghiyath al-Din Muhammad (fl. 1176–1200), ruler of the Ghorid dynasty in Khorāsān
• Ghīyāth al-Dīn Kaykhusraw bin Qilij Arslān, or Kaykhusraw I (died 1211), Seljuk Sultan of Rum
• Ghīyāth al-Dīn Kaykhusraw bin Kayqubād, or Kaykhusraw II (died 1246), Seljuk Sultan of Rum
• Ghīyāth al-Dīn Kaykhusraw bin Qilij Arslān, or Kaykhusraw III (died 1284), Seljuk Sultan of Rum
• Ghiyas ud din Balban (1200–1287), Turkic ruler of the Delhi Sultanate
• Ghiyath al-Din Tughluq (died 1325), founder of the Muslim Turkic Tughluq dynasty in India
• Ghiyasuddin Bahadur Shah (died 1328), ruler of Bengali kingdom of Lakhnauti
• Ghiyas al-Din ibn Rashid al-Din, (died 1336), Ilkhanate politician
• Ghiyasuddin Tughluq Khan (died 1389), Muslim Turkic ruler of the Tughlaq Dynasty
• Ghiyasuddin Baysunghur (1397–1433) son and associate of the Timurid ruler Shah Rukh in Herat
• Ghiyāth al-dīn Naqqāsh (fl. 1419–1422), the diarist of a Persian embassy to China
• Ghiyāth al-Dīn Jamshīd ibn Masʾūd al-Kāshī, or just Jamshīd al-Kāshī (c. 1380–1429), Persian astronomer and mathematician
• Ghiyasuddin Azam Shah (1390–1411), third Sultan of the first Ilyas Shahi dynasty of Bengal
• Ghiyāth al-Dīn ʿAlī Iṣfahānī, fifteenth century, scholar in Badakhshān
• Ghiyath Shah (1469–1500), second Sultan of the Khilji dynasty of Malwa
• Ghiyasuddin Mahmud Shah (deposed 1538), last sultan of the Hussain Shahi dynasty of Bengal
• Ghiyasuddin Bahadur Shah II (r. 1555–1561), Sultan of Bengal
• Ghiyasuddin Jalal Shah (died 1563), Sultan of Bengal
• Muhammed Ghiya'as ud-din (fl. 1766–1773), Sultan of the Maldives
• Musa Ghiatuddin Riayat Shah of Selangor (1893–1955), Sultan of Selangor
• Ghayasuddin Pathan (1897–1963), Bengali politician
• Ghiasuddin Ahmad (born 1927), Indian-Bengali politician
• Ghyasuddin Ahmed (1933–1971), Bengali lecturer and historian
• Ghayasuddin Siddiqui (born 1939?), British-Pakistani academic and political activist
• T. M. Giasuddin Ahmed (1937–2020), Bangladeshi politician and former minister
• Muhammad Gias Uddin (born 1952), Bangladeshi politician
• Gias Uddin Ahmed (1954–2002), Bangladeshi politician and army officer
• Giasuddin Molla (born 1956), Indian-Bengali politician
• Giasuddin Selim, Bangladeshi film director
• Giasuddin Al Mamun, Bangladeshi businessman and owner of Channel 1
• Giasuddin Quader Chowdhury, Bangladeshi politician
• Gias Uddin Chowdhury, Bangladeshi politician
• Gyasuddin Shaikh, Indian politician

• Ghiyasuddin International School, Malé, Maldives. – School named after Sultan Muhammed Ghiya'as ud-din.
• Giasuddin Islamic Model College, Narayanganj, Bangladesh. – School named after former MP Muhammad Gias Uddin.

• A. K. Muhammad Ghaus Uddin (died 2019), Bangladeshi politician