Waitangi Day commemorates a significant day in the history of New Zealand. It is a public holiday held each year on 6 February to celebrate the signing of the Treaty of Waitangi, New Zealand's founding document, on that date in 1840.

The Treaty of Waitangi was signed on 6 February 1840, in a marquee erected in the grounds of James Busby's house (now known as the Treaty house) at Waitangi in the Bay of Islands. The Treaty made New Zealand a part of the British Empire, guaranteed Māori rights to their land and gave Māori the rights of British subjects. There are differences between the Māori and English language versions of the Treaty, and virtually since 1840 this has led to debate over exactly what was agreed to at Waitangi. Māori have generally seen the Treaty as a sacred pact, while for many years Pākehā (the Māori word for New Zealanders of predominantly European ancestry) ignored it. By the early twentieth century, however, some Pākehā were beginning to see the Treaty as their nation's founding document and a symbol of British humanitarianism. Unlike Māori, Pākehā have generally not seen the Treaty as a document with binding power over the country and its inhabitants. In 1877 Chief Justice James Prendergast declared it to be a 'legal nullity', a position it held until the Treaty of Waitangi Act 1975, when it regained significant legal standing.