Ubaidullah Sindhi (10 March 1872 – 21 August 1944) was a political activist of the Indian independence movement and one of its vigorous leaders. According to Dawn, Karachi, Maulana Ubaidullah Sindhi struggled for the independence of British India and for an exploitation-free society in India. He was also Home Minister of first Provisional Government of India established in Afghanistan in 1915.

Ubaidullah Sindhi was the Life Member of Jamia Millia Islamia, A Central University in New Delhi, India. He served the Jamia Millia Islamia for a long period of time on a very low salary. A boys' hostel in Dr. Zakir Husain Hall of Boys' Residence in Jamia Millia Islamia has been named after him.

Ubaidullah was born on 10 March 1872 in a Sikh Jatt family in the district of Sialkot, Punjab, British India as Buta Singh Uppal. His father died four months before Ubaidullah was born, and the child was raised for two years by his paternal grandfather. Following the paternal grandfather's death, he was taken by his mother to the care of her father, at his maternal grandfather's house. Later, young Buta Singh was entrusted to the care of his uncle at Jampur Tehsil, Punjab, British India, when his maternal grandfather died. Buta Singh Uppal converted to Islam at age 15 and chose "Ubaidullah Sindhi" as his new name, and later enrolled in the Darul Uloom Deoband, where he was, at various times, associated with other noted Islamic scholars of the time, including Maulana Rashid Ahmad Gangohi and Maulana Mahmud Hasan Deobandi. Maulana Sindhi returned to the Darul Uloom Deoband in 1909, and gradually involved himself in the Pan-Islamic movement. During World War I, he was among the leaders of the Deoband School, who, led by Maulana Mahmud Hasan Deobandi, left India to seek support among other nations of the world for a Pan-Islamic revolution in India in what came to be known as the Silk Letter Conspiracy.

Ubaidullah had reached Kabul during the war to rally the Afghan Amir Habibullah Khan, and after a brief period there, he offered his support to Raja Mahendra Pratap's plans for revolution in British India with German support. He joined the Provisional Government of India formed in Kabul in December 1915, and remained in Afghanistan until the end of World War I, and then left for Russia. He subsequently spent two years in Turkey and, passing through many countries, eventually reached Hijaz (Saudi Arabia) where he spent about 14 years learning and pondering over the philosophy of Islam especially in the light of Shah Waliullah Dehlawi's works. In his career, he was a Pan-Islamic thinker.

When he was at school, a Hindu friend gave him the book Tufatul Hind to read. It was written by a converted scholar Maulana Ubaidullah of Malerkotla. After reading this book and some other books like Taqwiyatul Eeman and Ahwaal ul Aakhira, Ubaidullah's interest in Islam grew, leading eventually to his conversion to Islam. In 1887, the year of his conversion, he moved from Punjab to Sindh area where he was taken as a student by Hafiz Muhammad Siddique of Chawinda (Bhar Chandi Shareef). He subsequently studied at Deen Pur Shareef (a village near Khanpur, Distt Rahim Yar Khan) under Maulana Ghulam Muhammad, Where he delved deeper into Islamic education and training in the mystical order. In 1888, Ubaidullah was admitted to Darul Uloom Deoband, where he studied various Islamic disciplines in depth under the tutelage of noted Islamic scholars of the time including Maulana Abu Siraj, Maulana Rashid Ahmad Gangohi and Maulana Mahmud Hasan Deobandi. He took lessons in Sahih al-Bukhari and Tirmidhi from Maulana Nazeer Husain Dehalvi and read logic and philosophy with Maulana Ahmad Hasan Cawnpuri.

In 1891, Ubaidullah graduated from the Deoband school. In 1899, he left for Sukkur area in Sindh province. In 1909, at the request of Mahmud Hasan Deobandi, he returned to Deoband School in Uttar Pradesh. Here, he accomplished much for the student body, Jamiatul Ansaar. Ubaidullah was now very active in covert anti-British propaganda activities, which led to him alienating a large number of the Deoband School leaders. Subsequently, Ubaidullah moved his work to Delhi at Mahmud Hasan Deobandi's request. At Delhi, he worked with Hakim Ajmal Khan and Dr. Ansari. In 1912, he established a madrassah, Nazzaaratul Ma'arif to propagate Islam among the people.

With the onset of World War I in 1914, efforts were made by the Darul Uloom Deoband to forward the cause of Pan-Islam in British India with the help of the other sympathetic nations of the world. Led by Mahmud Hasan Deobandi, plans were sketched out for an insurrection beginning in the tribal belt of North-West Frontier Province of British India. Mahmud Hasan Deobandi, left India to seek the help of Galib Pasha, the Turkish governor of Hijaz, while at Hasan's directions, Ubaidullah proceeded to Kabul to seek Emir Habibullah's support there. Initial plans were to raise an Islamic army (Hizb Allah) headquartered at Medina, with an Indian contingent at Kabul. Maulana Hasan was to be the General-in-Chief of this army. Some of Ubaidullah's students went to Kabul to explore things before Ubaidullah arrived there. While at Kabul, Ubaidullah came to the conclusion that focusing on the Indian Freedom Movement would best serve the pan-Islamic cause. Ubaidullah had proposed to the Afghan Emir that he declare war against British India. Maulana Abul Kalam Azad is known to have been involved in the movement prior to his arrest in 1916.

Maulana Ubaidullah Sindhi and Mahmud Hasan Deobandi (principal of the Darul Uloom Deoband) had proceeded to Kabul in October 1915 with plans to initiate a Muslim insurrection in the tribal belt of British India. For this purpose, Ubaid Allah was to propose that the Amir of Afghanistan declare war against Britain while Mahmud Hasan Deobandi sought German and Turkish help. Hasan proceeded to Hijaz. Ubaidullah, in the meantime, was able to establish friendly relations with Emir Habibullah of Afghanistan. At Kabul, Ubaidullah along with some of his students, were to make their way to Turkey to join the Caliph's "Jihad" against Britain. But it was eventually decided that the pan-Islamic cause was to be best served by focusing on the Indian Freedom Movement.