Born in Brielle, Tromp was the oldest son of Harpert Maertensz, a naval officer and captain of the frigate "Olifantstromp ("Elephant Trunk")". The surname "Tromp" probably derives from the name of the ship; it first appeared in documents in 1607. His mother supplemented the family's income as a washerwoman. At the age of nine, Tromp went to sea with his father, and he was present in a squadron covering the Dutch main fleet fighting the Battle of Gibraltar in 1607.