Siraj-ud-Din Ali Khan (Urdu: سراج الدین علی خاں آرزو) (1687-1756), also known by his pen-name Arzu, was a Delhi-based poet, linguist and lexicographer of the Mughal Empire.
He taught Mir Taqi Mir, Mirza Muhammad Rafi Sauda, Mirza Mazhar Jan-e-Janaan and Najm-ud-Din Shah Mubarak Abroo.
He was the son of Sheikh Hisam-ud-Din, a soldier who held many high offices in the court of the Mughal emperor Aurangzeb.
He was highly proficient in Persian and Arabic, the two languages which he learned as a child.
Qamar-ud-Din, who was the prime minister at that time, gave him a suitable job.