Lajin, full royal name al-Malik al-Mansur Hussam al-Din Lajin al-Mansuri (الملك المنصور حسام الدين لاجين المنصورى; d. January 16, 1299, Cairo) was a Mamluk sultan of Egypt from 1296 to 1299. Originally Greek, he was a mamluk of Qalawun and had participated in the assassination of Qalawun's son the Sultan al-Ashraf Khalil. He also tried assassinating the Sultan al-Adil Kitbugha but failed. Kitbugha, fearing for his life, sent to him afterwards that he is ready to remove himself from the Sultanate for him to be the Sultan instead. Lajin agreed and became Sultan under the title al-Mansur Hussam al-Din, while Kitbugha was given a fief in the Levant.