The Wairarapa Fault is a right-lateral strike-slip fault with a reverse component on the southern North Island of New Zealand, running about 120 kilometres northeast from near Cook Strait through the Wairarapa valley behind Wellington. It is one of the major faults accommodating the oblique collision along the Hikurangi plate margin, where the Pacific Plate dives beneath the Australian Plate.
Because it lies close to the capital city of Wellington, the fault is a central concern for New Zealand's seismic hazard planning. Its motion combines large horizontal slip with uplift, and its most recent rupture raised marine terraces and shorelines by several metres, dramatically reshaping the local coastline.
The fault produced the 1855 Wairarapa earthquake, estimated at magnitude 8.2 and the strongest earthquake in New Zealand's recorded history. That event shifted the ground horizontally by up to 18 metres in places and lifted land around Wellington Harbour, creating new flat terrain that the growing city later built upon.