Maharana Hammir Singh (1302–1364), or Hammir, was a 14th-century ruler of Mewar in present-day Rajasthan, India. Hammir Singh, was a scion of the cadet branch Rana of the Guhila dynasty, who regained control of the region, re-established the dynasty after defeating the Tughlaq dynasty, and captured present-day Rajasthan from Muslim forces of Delhi and became the first of the 'Rana' branch to become the King of Mewar with title of Maharana. Hammir also became the progenitor of the Sisodia clan, a branch of the Guhila dynasty, to which every succeeding Maharana of Mewar has belonged.

Mewar during Rana Hammir's reign, was one of the few Hindu states that had withstood the Turkic invasions. According to John Darwin "Only in Mewar and in Vijaynagar had Hindu states withstood the deluge".

Mahavir Prasad Prashasti identify to Hammir as Vanquisher of Turushkas. After regaining Chittor, he built the Annapoorna Mata temple in Chittor Fort dedicated to Aai Birwadi. He also built the old temple of Roopnarayan Ji in Sewantri.

Ancestors of Hammir Singh connecting to the Guhila Rawal Branch of Chittor are:

Rana Laksha of Sisoda had nine sons, of whom the eldest was Ari Singh, who married Urmila, a Chandaana Chauhan Rajput lady from the village of Unnava near Kelwara. Rana Hammir was the only child of this couple.

At the turn of the 13th century, Alauddin Khilji attacked Chittorgarh, Rana Laksha and his sons joined the garrison at Chittorgarh to defend it against the invading army. Rana Laksha died along with his seven sons performing saka (fighting to death) at the end of Siege of Chittorgarh. Ruling Rawal branch of Chittorgarh ceased to exist, as they all died performing saka. Ajay Singh (son of Lakshman Singh) was wounded and was smuggled out of Chittorgarh to preserve the blood line. He reached Kelwara and recovered of his wounds there. There he found out about Hammir and called him from Unnava. Rana Hammir killed Bhil Chief Munja Balecha of Godwar, who was causing chaos in the nearby area. This event impressed his uncle and Hammir was chosen as the successor to the throne.

Lakshman Singh was Thakur of Sisoda village. He died along with his seven sons performing saka (fighting to death), while their women committed jauhar (self-immolation in preference to becoming enemy captives). Laksha was descended in direct patrician lineage from Bappa Rawal and hence belonged to the Gehlot (Guhilot) clan. Laksha came from the village of Sisoda near the town of Nathdwara and thus his children came to be known as Sisodia.

Khaljis allocated administration of Chittorgarh to Sonagara Maldev, ruler of the nearby state of Jalore. After becoming the Rana of Sisoda, Hammir pursued an aggressive scheme of recovering Mewar.