Tuamarina (often spelled Tua Marina) is a small town in Marlborough, New Zealand. State Highway 1 runs through the area. The Tuamarina River joins the Wairau River just south of the settlement. Picton is about 18 km to the north, and Blenheim is about 10 km to the south.

The name is a corruption of the Māori word Tuamarino, which means 'the calm beyond'. Dairy farming is the major economic activity,.The original Factory was the Waitohi Co-op which amalgamated with the Koromiko cheese factory and the Rai Valley Co-op to form the Marlborough Cheese Company in 1981. The new Company continued Waitohi's long history winning a number of awards Marlborough Cheese was taken over by Fonterra Dairy Company in 1999. it was destroyed by fire in 2004.

The Wairau Affray occurred in the area in 1843, resulting in 26 deaths.

The Wairau Plain is prone to flooding, and river conservation is necessary to keep the river under control. Significant floods have occurred in the Tuamarina area, such as one in December 1939.

Tuamarina is defined by Statistics New Zealand as a rural settlement. It covers 9.68 km (3.74 sq mi) and had an estimated population of 230 as of June 2024, with a population density of 24 people per km. It is part of the larger Tuamarina statistical area.

Historical population for Tuamarina settlement

Year	Pop.	±% p.a.
2006	267	—
2013	222	−2.60%
2018	237	+1.32%
Source:

Tuamarina had a population of 237 at the 2018 New Zealand census, an increase of 15 people (6.8%) since the 2013 census, and a decrease of 30 people (−11.2%) since the 2006 census. There were 87 households, comprising 117 males and 120 females, giving a sex ratio of 0.97 males per female. The median age was 45.8 years (compared with 37.4 years nationally), with 48 people (20.3%) aged under 15 years, 30 (12.7%) aged 15 to 29, 123 (51.9%) aged 30 to 64, and 39 (16.5%) aged 65 or older.

Ethnicities were 94.9% European/Pākehā, 12.7% Māori, 2.5% Asian, and 2.5% other ethnicities. People may identify with more than one ethnicity.

Although some people chose not to answer the census's question about religious affiliation, 63.3% had no religion, 27.8% were Christian and 1.3% had other religions.

Of those at least 15 years old, 30 (15.9%) people had a bachelor's or higher degree, and 33 (17.5%) people had no formal qualifications. The median income was $41,200, compared with $31,800 nationally. 30 people (15.9%) earned over $70,000 compared to 17.2% nationally. The employment status of those at least 15 was that 120 (63.5%) people were employed full-time, and 24 (12.7%) were part-time.

Tuamarina statistical area surrounds the settlement and also includes Rārangi. It covers 167.84 km (64.80 sq mi). It had an estimated population of 1,370 as of June 2024, with a population density of 8.2 people per km.

Historical population for Tuamarina statistical area

Year	Pop.	±% p.a.
2006	1,092	—
2013	1,185	+1.17%
2018	1,263	+1.28%
Source:

Tuamarina had a population of 1,263 at the 2018 New Zealand census, an increase of 78 people (6.6%) since the 2013 census, and an increase of 171 people (15.7%) since the 2006 census. There were 477 households, comprising 633 males and 633 females, giving a sex ratio of 1.0 males per female. The median age was 46.4 years (compared with 37.4 years nationally), with 249 people (19.7%) aged under 15 years, 162 (12.8%) aged 15 to 29, 648 (51.3%) aged 30 to 64, and 207 (16.4%) aged 65 or older.

Ethnicities were 92.6% European/Pākehā, 13.1% Māori, 1.9% Pasifika, 1.2% Asian, and 2.1% other ethnicities. People may identify with more than one ethnicity.

The percentage of people born overseas was 17.1, compared with 27.1% nationally.

Although some people chose not to answer the census's question about religious affiliation, 63.4% had no religion, 25.7% were Christian, 0.2% were Hindu, 0.5% were Buddhist and 1.7% had other religions.

Of those at least 15 years old, 186 (18.3%) people had a bachelor's or higher degree, and 174 (17.2%) people had no formal qualifications. The median income was $35,100, compared with $31,800 nationally. 192 people (18.9%) earned over $70,000 compared to 17.2% nationally. The employment status of those at least 15 was that 576 (56.8%) people were employed full-time, 150 (14.8%) were part-time, and 21 (2.1%) were unemployed.

Tua Marina School is a coeducational full primary (years 1–8) school with a decile rating of 7 and a roll of 92 as of August 2024. The school celebrated its 100th anniversary in 1971.

• Eileen Duggan, 1894–1972, poet.