The Manor of Rensselaerswyck, Manor Rensselaerswyck, Van Rensselaer Manor, or just simply Rensselaerswyck, is the name of a colonial estate—specifically, a Dutch patroonship and later an English manor—owned by the van Rensselaer family that is located in what is now mainly the Capital District of New York in the United States.

The estate is originally deeded by the Dutch West India Company in 1630 to Kiliaen van Rensselaer, a Dutch merchant and one of the company's original directors.

Rensselaerswyck extends for miles on each side of the Hudson River near present-day Albany. It includes most of what are now the present New York counties of Albany and Rensselaer, as well as parts of Columbia and Greene counties.

Under the terms of the patroonship, the patroon has nearly total jurisdictional authority, establishing civil and criminal law, villages, a church (in part to record vital records, which will not be done by the state until the late nineteenth century).

Tenant farmers are allowed to work on the land, but have to pay rent to the owners, and have no rights to property. In addition, the Rensselaers harvest timber from the property.

The patroonship is maintained intact by Rensselaer descendants for more than two centuries

It is split up after the death of Stephen van Rensselaer III in 1839

His son Stephen Van Rensselaer IV, the 10th and last patroon, receives the bulk of his holdings; son William receives some lands east of the Hudson.

At his death, Steven van Rensselaer III's land holdings made him the tenth-richest American in history to date.

Under his sons tenant farmers begin protesting the manor system, part of a sweeping challenge in New York State.

Under financial, judicial, and political pressure from this anti-rent movement Stephen IV and William sell off most of their land, ending the patroonship in the 1840s.

For length of operations, it is the most successful patroonship established under the West India Company system.