The Halve Maen (English: Half Moon) was the name of a Dutch East India Company yacht which sailed in what is now New York harbor in September, 1609. It was commissioned by the Dutch Republic to covertly find an eastern passage to China. The ship was captained by Henry Hudson who was an Englishman in the service of the Dutch Republic. The Halve Maen sailed from Amsterdam to the Barents Sea, turning westward to traverse the Atlantic Ocean sailing from Newfoundland to south in search of the Northwest Passage. In his 1625 book New World , which contains invaluable extracts from Hudson’s lost journal, Johannes de Laet, a director of the West India Company, writes that they "bent their course to the south until, running south-southwest and southwest by south, they again made land in latitude 41° 43’, which they supposed to be an island, and gave it the name of New Holland, but afterwards discovered that it was Cape Cod".

From there they sailed south to the Chesapeake and then went north along the coast navigating first the Delaware Bay and, subsequently, the bay of the river which Hudson named the Mauritius River, for Holland's Lord-Lieutenant Maurits. The Halve Maen sailed up Hudson’s river as far as Albany, New York, where the crew determined the water was too narrow and too shallow for farther progress. Concluding then that the river was also not a passage to the east, Hudson exited the river, naming the natives that dwelled on either side of the Mauritus estuary the Manahata. Leaving the estuary, he sailed north-eastward, never realizing that what are now the islands of Manhattan and Long Island were islands, and crossed the Atlantic to England where he sailed into Dartmouth harbor with the Dutch East India Company yacht and crew. A map of 1610 depicts the Manahatas west and east of Hudson’s river and from which the name Manhattan originates.

A replica of the Halve Maen (officially Anglicized as Half Moon) was constructed in Albany, New York in 1989 by the New Netherland Museum. The museum contracted with the late Nicholas S. Benton to design and build the replica. Mr. Benton, a master ship-rigger and shipwright, was president of the Rigging Gang of Middletown (Rhode Island), which specialized in colonial ship restoration and design. To prepare for building the Half Moon, a $1 million project, he visited maritime museums in the Netherlands and the United States. After his untimely death while assisting with the rigging of another vessel, the construction of the Half Moon was completed by the New Netherland Museum. The year 2009 will mark the 400th anniversary of the Half Moon's voyage.

The replica ship sails in and around the Hudson River and serves as a traveling museum that conducts programs for youth and adults about the history of the Dutch colony called New Netherland. With its Voyages of Discovery and 4th and 7th grade Interdisciplinary Curricula, the ship pursues a comprehensive education program. A non-for-profit organization, the Half Moon is run by a crew of volunteers that range in age from their teens to octogenarians.

The Town of Halfmoon in New York is named after the ship. An eight foot tall model of the Halve Maen serves as a weathervane on top of the SUNY System Administration Building in Albany, New York.