Emergency services were called to Settlers Way, the town of Ōkaihau's main street, late on Tuesday night.
"We believe the collision between a cyclist and vehicle has occurred between 10pm and 10.15pm on that road," Detective Senior Sergeant Kevan Verry said.
"Tragically, it has resulted in a 19-year-old dying from his injuries at the scene."
Police said they were looking for the person responsible.
"A young man has lost his life, and it's important that anyone in the community with information does the right thing and speaks up now," Verry said.
One resident told RNZ she saw a pool of blood on the road outside Ōkaihau College this morning, and a second patch about 50 to 100 metres away marked with neon spray paint.
She said she saw police speaking to a staff member at the school, due to reopen on Friday after the summer break.
Police were searching for a car with obvious signs of damage and Verry urged anyone with information to speak up.
A crash investigator examined the scene early this morning and a criminal investigation was under way.
"Detectives are working to piece together who is responsible. Police will be in the Ōkaihau township as part of our investigation, seeking witnesses and further information."
Victim Support was helping the cyclist's family.
"Our thoughts are with the family at this difficult time and with what they are going through."
Anyone who witnessed the lead-up or aftermath of the hit-and-run, or who had any information, should contact police, Verry said.
People could contact police online or call 105, quoting reference number 250129/0360.
Information could also be passed on anonymously via Crime Stoppers on 0800 555 111.
