Mangatāwhiri is a locality about 10 km north-east of Pōkeno and 7 km west of Mangatangi in the Waikato District in the North Island of New Zealand.

The Mangatawhiri area unit, which is much larger than the locality and includes Mangatangi, had a population of 1,533 at the 2013 New Zealand census, an increase of 153 people since the 2006 census. There were 825 males and 708 females. 83.1% were European/Pākehā, 14.8% were Māori, 4.1% were Pacific peoples and 4.5% were Asian. The locality is in meshblocks 0841700 and 0843401, which had a population of 117 people in 48 households in the census.

The New Zealand Ministry for Culture and Heritage gives a translation of "tāwhiri tree stream" for Mangatāwhiri.

The Mangatāwhiri castle is a prominent building on Mangatawhiri Road which once housed the Castle Cafe but is now empty.

Mangatāwhiri River flows south from the Hunua Ranges through Mangatāwhiri, and joins the Waikato River near Mercer.

During the 19th Century New Zealand Wars, Mangatāwhiri (specifically the Mangatāwhiri River) was set down by the second Māori King as an 'aukati', or demarcation line, indicating the boundary between the lands controlled by the Government (to the north of the river) and those controlled by the then nascent King Movement. Responding to the movement of British colonial troops southward from Auckland, King Tāwhiao stated that should these same troops cross the Mangatāwhiri River, then war would then ensue. On the 12th of July 1863, the British forces led by General Cameron duly crossed the river and thus commenced the invasion of the Waikato. This led to some of the most significant conflicts of the 19th century colonisation of New Zealand.

In the late 19th century, Mangatāwhiri was a major location for the kauri gum digging trade.

Mangatawhiri School is a co-educational state full primary school covering years 1 to 8, with a roll of 180 as of August 2024. The school started in the Lyons Homestead in the 19th century, and was moved to McKenzie Road in 1925. In 1962 a new school was built on the same site, and it has since been expanded to seven classrooms.