Ranjit Singh (13 November 1780 – 27 June 1839) was the founder and first maharaja of the Sikh Empire, in the northwest Indian subcontinent, ruling from 1801 until his death in 1839.

Born to Maha Singh, the leader of the Sukerchakia Misl, Ranjit Singh survived smallpox in infancy but lost sight in his left eye. At the age of ten years old, he fought his first battle alongside his father. After his father died around Ranjit's early teenage years, he became leader of the Misl. Ranjit was the most prominent of the Sikh leaders who opposed Zaman Shah, the ruler of Durrani Empire, during his third invasion. After Zaman Shah's retreat in 1799, he captured Lahore from the Sikh triumvirate which had been ruling it since 1765. At the age of 21, he was formally crowned at Lahore.

Before his rise, the Punjab had been fragmented into a number of warring Sikh (known as misls), Muslim and Hindu states. A large part of Punjab was under direct Durrani control. By 1813, Ranjit Singh had successfully annexed the Sikh misls and taken over the local kingdoms; the following decades saw the conquest of Durrani Afghan-ruled territories of Multan, Kashmir and Peshawar into his expanding Sikh Empire. Ranjit Singh established friendly relations with the British.

Ranjit Singh's reign introduced reforms, modernisation, investment in infrastructure and general prosperity. His Khalsa army and government included Sikhs, Hindus, Muslims and Europeans. His legacy includes a period of Sikh cultural and artistic renaissance, including the rebuilding of the Harmandir Sahib in Amritsar as well as other major gurdwaras, including Takht Sri Patna Sahib, Bihar and Hazur Sahib Nanded, Maharashtra under his sponsorship. He also founded the Order of the Propitious Star of Punjab in 1837. Ranjit Singh was succeeded by his son Kharak Singh after his death in 1839.

Ranjit Singh was born in a Sandhawalia Jat Sikh family on 13 November 1780 to Maha Singh and Raj Kaur in Gujranwala, Punjab region (present-day Punjab, Pakistan). His mother Raj Kaur was the daughter of Sidhu Jat Sikh ruler Raja Gajpat Singh of Jind. Upon his birth, he was named Buddh Singh after his ancestor who was first in line to take the Amrit Sanchaar. The child's name was changed to Ranjit (literally, "victor in battle") Singh ("lion") by his father to commemorate his army's victory over the Chattha chief Pir Muhammad of Chattha State.

Singh contracted smallpox as an infant, which resulted in the loss of sight in his left eye and a pockmarked face. He was short in stature, unattractive, never schooled, and did not learn to read or write anything beyond the Gurmukhi alphabet. However, he was trained at home in horse riding, musketry and other martial arts.

At age 12, his father died. He then inherited his father's Sukerchakia Misl estates and was raised by his mother Raj Kaur, who, along with Lakhpat Rai, also managed the estates. The first attempt on his life was made when he was 13, by Hashmat Khan, but Ranjit Singh prevailed and killed the assailant instead. At age 18, his mother died and Lakhpat Rai was assassinated, and thereon he was aided by his mother-in-law from his first marriage.

After the death of Aurangzeb in 1707, the Mughal Empire fell apart and declined in its ability to tax or govern most of the Indian subcontinent. In the northwestern region, particularly the Punjab, the creation of the Khalsa community of Sikh warriors by Guru Gobind Singh accelerated the decay and fragmentation of the Mughal power in the region. Raiding Afghans attacked the Indus river valleys but met resistance from both organised armies of the Khalsa Sikhs as well as irregular Khalsa militias based in villages. The Sikhs had appointed own zamindars, replacing the previous Muslim revenue collectors, which provided resources to feed and strengthen the warriors aligned with Sikh interests. Meanwhile, colonial traders and the East India Company had begun operations in India on its eastern and western coasts.