HELDER, a fortified seaport town on a projecting tongue of land at the N. extremity of North Holland. It is separated by the Mars diep from the island of Texel, and stands 40 miles N. W. of Amsterdam. It commands the Mars diep, the channel to the Zuider Zee. East of the town is the fine harbour of Nieuwe diep, accessible to the largest ships. It is connected with Amsterdam by the Helder Canal, by means of which the largest merchant vessels reach Amsterdam without encountering the difficult navigation of the Zuider Zee. This canal is 50 miles in length, 125 feet broad at the surface, and 21 feet deep. The Dutch admiral, Van Tromp, was killed in an engagement off Helder in 1693. It was taken by the British under Sir Ralph Abercrombie in 1799. Pop. about 2900.