Union of Utrecht
Five northern provinces, later followed by most cities in Brabant and Flanders, then signed the Union of Utrecht on 23 January, confirming their unity. William was initially opposed to the Union, as he still hoped to unite all provinces. Nevertheless, he formally gave his support on 3 May. The Union of Utrecht would later become a "de facto" constitution, and would remain the only formal connection between the Dutch provinces until 1797.