Gijsbrecht IV of Amstel

They derived their name from their castle on the River Amstel, and tried to create an independent principality between Utrecht and Holland.

To this end Gijsbrecht IV—along with the other powerful lords Zweder of Abcoude, Arnoud of Amstel, and Herman VI of Woerden—instigated a revolt against Floris V, Count of Holland, and John I, Bishop-Elect of Utrecht.

They held lands on the border with the adjacent Bishopric of Utrecht—the area of Amsterdam, Abcoude, IJsselstein, and Woerden—at the expense of the bishop, and were backed by the craftsmen of Utrecht, the peasants of Kennemerland—Alkmaar and surroundings—Waterland, Amstelland and the West Frisians.

The bishop of Utrecht eventually (in 1279 or 1281) also added the lands of the rebellious lords to Floris's territory in retribution.

Gijsbrecht changed sides when opportune, and some accounts allege him to have been involved in Floris's later capture and assassination.