The Sikh Empire ended in 1849 after the Second Anglo-Sikh War.
The British East India Company annexed the Punjab on 29 March 1849, following the Sikh defeat in the conflict that began in 1848. The annexation ended the independent Sikh kingdom created under Maharaja Ranjit Singh and brought Punjab under British rule.
Ranjit Singh had built a powerful state in northwestern South Asia, centered on Lahore, by uniting several Sikh misls and expanding into neighboring territories. After his death in 1839, succession disputes and political instability weakened the empire.
The First Anglo-Sikh War ended with the Treaty of Lahore in 1846, but Sikh sovereignty continued for three more years. That distinction is why 1849, rather than 1846, marks the empire’s final end.