Alwar or Ulwar was a princely state in India during the time of British rule, in what is now Rajasthan.

The state was founded by Pratap Singh (1740-1791), a Rajput of ancient lineage, and increased by his adopted son Bakhtawar Singh. The latter joined the British against the Mahrattas, and in 1803, after the battle of Laswari (Nov. 1), signed a treaty of offensive and defensive alliance with the British government. A few years later, owing to his armed intervention in Jaipur, a fresh engagement was made, prohibiting him from political intercourse with other states without British consent. In 1857 the raja Binni Singh sent a force of Muslims and Rajputs to relieve the British garrison in Agra; the Muslims, however, deserted, and the rest were defeated by the mutineers.

Alwar was merged into the state of Rajasthan following independence in 1947.