Mill Green Museum is a working watermill in Hatfield, Hertfordshire, England.
The building is listed grade II* and dates from the 17th century. The mill uses the power of the River Lea, and the site has been used for milling since the Domesday Book.It is managed by Welwyn Hatfield Borough Council. As of 2019, admission is £3.50 for adults and £0.50 for children under 16.
Its heart is a working watermill, with 18th and 19th century wooden machinery restored to full working order. It is in regular use to grind organic wheat for a local bakery and for retail sale. Visitors can explore the mill, see it working and chat to the miller on duty. Flour is sold in various sizes.
The mill also houses the local museum in the old miller's house. Three galleries show changing displays of art and local history.
Mill Green runs craft and baking workshops, children's activities and a school visit service
