Mangatainoka is a small settlement in the Tararua District of New Zealand's North Island. It is located on the banks of the Mangatainoka River, 5 km (3.1 mi) north of Pahiatua.

Mangatainoka is home to the Tui Brewery, which ceased brewing in 2021. It also has a golf course.

The greater Mangatainoka area, as defined by Statistics New Zealand, covers an area of 496.81 km (191.82 sq mi). The statistical area includes the settlement of Papatawa, and surrounds but does not include the towns of Woodville and Pahiatua.

Mangatainoka statistical area had an estimated population of 1,990 as of June 2024, with a population density of 4.0 people per km.

Historical population

Year	Pop.	±% p.a.
2006	1,752	—
2013	1,749	−0.02%
2018	1,743	−0.07%
Source:

Mangatainoka had a population of 1,743 at the 2018 New Zealand census, a decrease of 6 people (−0.3%) since the 2013 census, and a decrease of 9 people (−0.5%) since the 2006 census. There were 678 households, comprising 888 males and 855 females, giving a sex ratio of 1.04 males per female. The median age was 42.3 years (compared with 37.4 years nationally), with 360 people (20.7%) aged under 15 years, 279 (16.0%) aged 15 to 29, 858 (49.2%) aged 30 to 64, and 246 (14.1%) aged 65 or older.

Ethnicities were 92.6% European/Pākehā, 14.5% Māori, 1.0% Pasifika, 1.7% Asian, and 0.9% other ethnicities. People may identify with more than one ethnicity.

The percentage of people born overseas was 7.7, compared with 27.1% nationally.

Although some people chose not to answer the census's question about religious affiliation, 49.9% had no religion, 38.6% were Christian, 1.5% had Māori religious beliefs, 0.2% were Muslim and 1.2% had other religions.

Of those at least 15 years old, 198 (14.3%) people had a bachelor's or higher degree, and 327 (23.6%) people had no formal qualifications. The median income was $32,700, compared with $31,800 nationally. 201 people (14.5%) earned over $70,000 compared to 17.2% nationally. The employment status of those at least 15 was that 771 (55.7%) people were employed full-time, 225 (16.3%) were part-time, and 42 (3.0%) were unemployed.

In 2018, 7.2% worked in manufacturing, 6.0% worked in construction, 3.3% worked in hospitality, 3.6% worked in transport, 6.9% worked in education, and 8.1% worked in healthcare.

As of 2018, among those who commute to work, 55.9% drove a car, 2.4% rode in a car, 0.6% use a bike, and 0.6% walk or run. No one commuted by public transport.

Mangatainoka railway station and railway line opened to Mangatainoka in August 1897 and the settlement was briefly the terminus of the Wairarapa Line until the final section to a junction with the Palmerston North–Gisborne Line in Woodville was opened on 11 December 1897. Passenger train services were originally provided by the Napier Express until it was re-routed via the former Wellington and Manawatu Railway Company's western line through the Kāpiti Coast and Horowhenua in early 1909.

It was replaced by the Wairarapa Mail, which served Mangatainoka until 1948, when it was fully replaced by the NZR RM Wairarapa class railcars that had begun operating some services in 1936. Standard and 88 seater class railcars also operated to Mangatainoka, especially after the Wairarapa railcars were withdrawn in the wake of the Rimutaka Incline's 1955 closure. Carriage trains through Mangatainoka were reintroduced in 1964 but did not fully replace the railcars until 1977.

As roads in the area improved through the 1980s, passenger numbers declined and all services north of Masterton ceased on 29 July 1988. Since this time, only freight trains have regularly operated through Mangatainoka; passenger services have been limited to occasional excursions, typically organised by enthusiast societies.

Mangatainoka School is a co-educational state primary school for Year 1–8 students, with a roll of 54 as of August 2024.