Adhai Din Ka Jhonpra is a large and imposing structure in the city of Ajmer in Rajasthan, India .

It is one of the oldest mosques in India, and the oldest surviving monument in Ajmer.

Captured and appropriated first by Abu Bakr of Herat and again by Qutb-ud-Din-Aibak in 1192 CE, the mosque is an example of early Islamic architecture. The structure was completed in 1199 CE and was further enlarged by Iltutmish of Delhi in 1213 CE. An early example of Islamic architecture, most of the building was constructed by Hindu masons, under the supervision of Afghan managers. The mosque retained most of the original Indian features, especially on the ornate pillars.

The structure was used as a mosque up to 1947. After the independence of India, the structure was turned over to the Jaipur circle of ASI (Archaeological Survey of India) and is today visited by people of all religions, as a fine example of a mix of Indian, Hindu, Muslim and Jain architectures.