De Modderige Bol is a Hollow Post mill in Goëngahuizen, Friesland, Netherlands which has been restored to working order.

[2] Until 1952, the mill drained the polder Adamse, which had an area of 150 pondemaat (55 ha; 140 acres).

A further restoration was undertaken in 1978 by millwrights Bouwbedrijf Van Zuiden of Tjerkwerd.

It is a hollow post mill on a single storey square roundhouse.

Each revolution of the screw lifts 106 litres (23 imp gal) of water.