Sandrina Louisa Geertruida Holthuysen (1824 – 1895) was a Dutch art collector and founder of the Museum Willet-Holthuysen in Amsterdam.

Her father died in 1858 and in 1861 she married Abraham Willet and they proceeded to live a bohemian lifestyle, enjoying travel and art collecting.

The art collection included items bought by her, of which the most expensive painting was a still-life by Blaise Alexandre Desgoffe that cost 5,000 guilders.

[1] Holthuysen died childless in Amsterdam in 1895, a few years after her husband.

Her house and its contents, including the artworks, were left to the City of Amsterdam, conditional upon the building being used as a museum named after her and her husband.