William Hemingway Mills[a] (1834-1918) was a British civil engineer known for his work with the Great Northern Railway of Ireland (GNR(I)) from its formation in 1876 until his retirement in 1910.

Mills undertook work in Scotland, Andalusia and Mexico before becoming Chief Engineer of the GNR(I) from its formation in 1876.

[1] Mills was to introduce a polychromatic brick style to many buildings in his designs for the GNR(I).

[1] Mills died at his home in Glenageary, County Dublin on 12 January 1918, aged c.

This article about an engineer, inventor or industrial designer from England is a stub.