The crash happened on State Highway 27 on August 31.

An Auckland teenager critically injured in a head-on crash in the Waikato has died in hospital.

Her 21-year-old partner, from Parnell, remains in a critical state in Waikato Hospital following the crash with an Army vehicle near Matamata last Friday night.

Waikato police Senior Sergeant Simon Cherry confirmed the 17-year-old woman, who was a passenger in a Ford Mondeo, died in hospital on Wednesday.

The crash happened on State Highway 27, in the Matamata district, at 8.45pm.

Initial indications show a Ford Mondeo, driven by the 21-year-old man, was heading south and overtaking several vehicles in a line of traffic when it crashed head-on into an oncoming Army personnel carrier, Senior Sergeant Pete van de Wetering said earlier.

The couple from Auckland both suffered critical head injuries and were flown by rescue helicopter to hospital.

A woman driving the Army vehicle was also injured.

Police Serious Crash unit are continuing investigations into the crash.

It comes after a carnage week on the region's roads that saw two pedestrians hit and killed and another driver die in a crash in Huntly.

"It shows how important having patience is on our roads - it's not worth it for the sake of minutes," van de Wetering said.

"Never overtake unless you're certain enough to do so."