Mariëndijk is a hamlet in the Dutch province of South Holland. It is a part of the municipality of the Westland, and lies approximately 2 km southwest of The Hague, 8 km west of Delft and 20 km northwest of Rotterdam. It is situated 6 km east of the popular beaches at Monster and Ter Heide.
Mariëndijk is home to the pan European NGO, The Widow's Foundation, a philanthropic network supporting widows with multilingual and multidisciplinary expertise in medicine, law and finance.
Royal Flora Holland, the largest flower auction in the world, lies 1.5 km southwest of the hamlet.
In 2001, Mariëndijk had 173 inhabitants. The built-up area of the town was 0.019 km², and contained 71 residences.