Marlborough Anniversary Day is observed in the former historic province of Marlborough, New Zealand, on the Monday closest to November 1. This day commemorates the establishment of the Marlborough Province, which separated from Nelson Province in 1859. The region, located in the northeast of the South Island, was first explored by Captain James Cook in the 1770s, leading to the initial European contact with local Māori iwi. The fertile Wairau Valley attracted settlers in the 1840s, although this expansion led to the Wairau Affray in 1843, a significant conflict between British settlers and the Ngāti Toa tribe. Despite the brief existence of the provincial system, former provinces like Marlborough continue to celebrate their anniversary days, marking the arrival of the first settlers or the establishment of provincial governance.