The Castle Hill rebellion of 1804 was a convict rebellion in the Castle Hill area of Sydney, against the colonial authorities of the British colony of New South Wales. The rebellion culminated in a battle fought between convicts and the colonial forces of Australia, on 5 March 1804 at Rouse Hill. It was dubbed the Second Battle of Vinegar Hill after the first Battle of Vinegar Hill, which had taken place in 1798 in Ireland. The incident was the first major convict uprising in Australian history to be suppressed under martial law.

On 4 March 1804, according to the official accounts, 233 convicts, led by Philip Cunningham (a veteran of the Irish Rebellion of 1798, as well as a mutiny on the convict transport ship Anne), escaped from a prison farm, intent on "capturing ships to sail to Ireland". In response, martial law was quickly declared in the colony. The mostly Irish rebels, having gathered reinforcements, were hunted by the colonial forces until they were caught on a hillock nicknamed Vinegar Hill on 5 March 1804. While negotiating under a flag of truce, Cunningham was arrested. The troops then charged, and the rebellion was crushed. Nine of the rebel leaders were executed, and hundreds were punished, before martial law was finally revoked a week after the battle.