Cornelius Essex was an English buccaneer who took part in Captain Bartholomew Sharp's privateering expedition, the "Pacific Adventure", during the late 1670s. Although much of his early life is unknown, he is first recorded being brought with his ship, the Great Dolphin, to Port Royal by HMS Hunter in November 1679 and tried with twenty of his crew for "riotously comporting themselves" as well as charges of looting the plantation of a Major Samuel Jenck's of St. James' parish for which two men were sentenced to death. Essex, as did the other Captains, held a commission by the Jamaican government that granted them permission to cut logwood in Honduras and left Port Morant in December 1679 with Captain John Coxon, Robert Allison, Thomas Mackett, Jean Rose and a Captain Bournano and rendezvoused at the Isles of Pines near eastern Panama shortly after. Following the election of Coxon as head of the party, the privateers traced the old route Sir Henry Morgan had taken in his raid on Portobello in 1668. After anchoring at a deserted cay, he was one of the privateers that participated in the overland assault on the Spanish stronghold and was among thirty others killed in a surprise attack against the garrison.