Ibn Khaldun (; Arabic: أبو زيد عبد الرحمن بن محمد بن خلدون الحضرمي, Abū Zayd ‘Abd ar-Raḥmān ibn Muḥammad ibn Khaldūn al-Ḥaḍramī; 27 May 1332 – 17 March 1406, 732-808 AH) was an Arab sociologist, philosopher, and historian widely acknowledged to be one of the greatest social scientists of the Middle Ages, and considered by many to be the father of historiography, sociology, economics, and demography studies.

His best-known book, the Muqaddimah or Prolegomena ("Introduction"), which he wrote in six months as he states in his autobiography, influenced 17th-century and 19th-century Ottoman historians such as Kâtip Çelebi, Mustafa Naima and Ahmed Cevdet Pasha, who used its theories to analyze the growth and decline of the Ottoman Empire. Ibn Khaldun interacted with Tamerlane, the founder of the Timurid Empire.

Recently, Ibn Khaldun's works have been compared with those of influential European philosophers such as Niccolò Machiavelli, Giambattista Vico, David Hume, G. W. F. Hegel, Karl Marx, and Auguste Comte as well as the economists David Ricardo and Adam Smith, suggesting that their ideas found precedent (although not direct influence) in his. He has also been influential on certain modern Islamic thinkers (e.g. those of the traditionalist school), as well as on Reaganomics.