St Andrews is a small town in the south Canterbury region of New Zealand's South Island. It is located on State Highway 1 five kilometres south of Pareora and 17 kilometres south of Timaru. It was linked to Timaru by rail in 1876, and grew after the subdivision of the Pareora Run. It remains a rural service town.

Saint Andrews is described as a rural settlement by Statistics New Zealand, and covers 0.59 km (0.23 sq mi). It had an estimated population of 210 as of June 2024, with a population density of 356 people per km. The settlement is part of the larger Lyalldale statistical area.

Historical population for Saint Andrews

Year	Pop.	±% p.a.
2006	177	—
2013	180	+0.24%
2018	195	+1.61%
Source:

Saint Andrews had a population of 195 at the 2018 New Zealand census, an increase of 15 people (8.3%) since the 2013 census, and an increase of 18 people (10.2%) since the 2006 census. There were 72 households, comprising 105 males and 90 females, giving a sex ratio of 1.17 males per female. The median age was 50.1 years (compared with 37.4 years nationally), with 30 people (15.4%) aged under 15 years, 27 (13.8%) aged 15 to 29, 102 (52.3%) aged 30 to 64, and 39 (20.0%) aged 65 or older.

Ethnicities were 95.4% European, 13.8% Māori, 1.5% Asian, and 1.5% other ethnicities. People may identify with more than one ethnicity.

Although some people chose not to answer the census's question about religious affiliation, 55.4% had no religion, and 33.8% were Christian.

Of those at least 15 years old, 6 (3.6%) people had a bachelor's or higher degree, and 57 (34.5%) people had no formal qualifications. The median income was $23,900, compared with $31,800 nationally. 15 people (9.1%) earned over $70,000 compared to 17.2% nationally. The employment status of those at least 15 was that 78 (47.3%) people were employed full-time, 24 (14.5%) were part-time, and 9 (5.5%) were unemployed.

The Lyalldale statistical area includes Saint Andrews and covers 109.54 km (42.29 sq mi). It had an estimated population of 780 as of June 2024, with a population density of 7.1 people per km.

Historical population for Lyalldale

Year	Pop.	±% p.a.
2006	588	—
2013	636	+1.13%
2018	687	+1.55%
Source:

Lyalldale had a population of 687 at the 2018 New Zealand census, an increase of 51 people (8.0%) since the 2013 census, and an increase of 99 people (16.8%) since the 2006 census. There were 243 households, comprising 369 males and 315 females, giving a sex ratio of 1.17 males per female. The median age was 43.3 years (compared with 37.4 years nationally), with 144 people (21.0%) aged under 15 years, 99 (14.4%) aged 15 to 29, 339 (49.3%) aged 30 to 64, and 105 (15.3%) aged 65 or older.

Ethnicities were 94.3% European/Pākehā, 9.6% Māori, 0.9% Pasifika, 2.6% Asian, and 1.7% other ethnicities. People may identify with more than one ethnicity.

The percentage of people born overseas was 13.5, compared with 27.1% nationally.

Although some people chose not to answer the census's question about religious affiliation, 50.7% had no religion, 36.7% were Christian, 0.9% were Hindu, 0.4% were Buddhist and 1.7% had other religions.

Of those at least 15 years old, 54 (9.9%) people had a bachelor's or higher degree, and 141 (26.0%) people had no formal qualifications. The median income was $31,800, compared with $31,800 nationally. 69 people (12.7%) earned over $70,000 compared to 17.2% nationally. The employment status of those at least 15 was that 303 (55.8%) people were employed full-time, 87 (16.0%) were part-time, and 18 (3.3%) were unemployed.

St Andrew's School is a full primary school serving years 1 to 8, with a roll of 100 students as of August 2024. The school opened in 1881.