Niezijl (Dutch: [ˈnizɛil]; Gronings: Nijziel), historically Bomsterzijl (probably from bom, meaning 'low, water-enclosed piece of land'),[3] is a village in the municipality of Westerkwartier in the province of Groningen in the Netherlands.

During the Eighty Years' War, the Bomsterschans near Niezijl was the only support point for the Staatsgezinden in the province of Groningen for a while.

Several Spanish attempts to conquer the sconce (including from Kommerzijl) failed, see Siege of Niezijl (1581).

After having continued to exist for a number of years below the legal standard of 52 pupils, the school merged in 1996 with CBS De Regenboog from Grijpskerk.

The current Reformed Church of Niezijl dates from 1661 and replaced a cheap building from 1650 that soon proved too small.