Brightwater (Māori: Wairoa) is a town 20 kilometres (12 mi) southwest of Nelson in Tasman district in the South Island of New Zealand. It stands on the banks of the Wairoa River. Brightwater was first named Spring Grove. Alfred Saunders, the owner of a local flax mill situated on the banks of the Wairoa River and a prominent temperance activist, renamed it Brightwater because of the clarity of the water in Wairoa River. The settlement was named in 1855, but the area was settled as early as 1843.

Brightwater was the birthplace of Nobel Prize-winning scientist, the "father of nuclear physics", Ernest Rutherford, and has an elaborate Lord Rutherford Birthplace memorial on Lord Rutherford Road.

The Brightwater statistical area covers 4.67 km (1.80 sq mi). It had an estimated population of 2,390 as of June 2024, with a population density of 512 people per km.

Historical population

Year	Pop.	±% p.a.
2006	1,827	—
2013	1,794	−0.26%
2018	2,133	+3.52%
Source:

Before the 2023 census, Brightwater had a larger boundary, covering 4.84 km (1.87 sq mi). Using that boundary, Brightwater had a population of 2,133 at the 2018 New Zealand census, an increase of 339 people (18.9%) since the 2013 census, and an increase of 306 people (16.7%) since the 2006 census. There were 744 households, comprising 1,080 males and 1,056 females, giving a sex ratio of 1.02 males per female. The median age was 38.7 years (compared with 37.4 years nationally), with 525 people (24.6%) aged under 15 years, 300 (14.1%) aged 15 to 29, 1,005 (47.1%) aged 30 to 64, and 303 (14.2%) aged 65 or older.

Ethnicities were 95.2% European/Pākehā, 8.7% Māori, 1.8% Pasifika, 1.1% Asian, and 1.7% other ethnicities. People may identify with more than one ethnicity.

The percentage of people born overseas was 12.2, compared with 27.1% nationally.

Although some people chose not to answer the census's question about religious affiliation, 62.6% had no religion, 28.6% were Christian, 0.1% had Māori religious beliefs, 0.1% were Hindu, 0.1% were Buddhist and 1.1% had other religions.

Of those at least 15 years old, 243 (15.1%) people had a bachelor's or higher degree, and 321 (20.0%) people had no formal qualifications. The median income was $36,100, compared with $31,800 nationally. 267 people (16.6%) earned over $70,000 compared to 17.2% nationally. The employment status of those at least 15 was that 870 (54.1%) people were employed full-time, 294 (18.3%) were part-time, and 33 (2.1%) were unemployed.

Brightwater School is a year 1 to 8 primary school founded in 1888, with a roll of 255 as of August 2024. The school campus has a dental clinic, reading recovery building, two sports fields, two playgrounds, a hard court area, a large shade structure and a swimming pool.

Four other schools previously operated in the area: Brightwater School for Girls (1881–1889), River Terrace School (1855–1920), Spring Grove School (1845–1974), and Waimea West School (1846–1938).

Brightwater is mainly an agricultural town. Because of its climate of little rain, it is hot from October through March, and it commonly experiences frosts during the winter. The main agriculture of the area is wine growing.

Brightwater's main recreational area is the Brightwater Domain. The Domain includes the town hall, a skatepark, a playground, tennis courts and several playing fields.

Brightwater has a small number of sports teams (mainly rugby teams), the most famous of which being the Wanderers, the Brightwater rugby team.

• Ernest Rutherford (1871–1937), physicist and Nobel Laureate
• Nate Wilbourne (born 2008), environmentalist and politician

• Media related to Brightwater at Wikimedia Commons