The Southland Wind Farm, also referred to as the Slopedown Wind Farm, is a proposed wind farm near Wyndham in the Southland district of New Zealand. If built it would be the largest wind farm in New Zealand. A wind farm on this site was first proposed in 2008, but did not progress. The idea was revived in 2023 by Contact Energy.

The project is currently seeking resource consent, and is opposed by some nearby residents mainly on its visual impact.

The latest version of the proposal, by Contact Energy, is for 55 turbines that are 220 metres base to tip, with a total a maximum generation of 300MW. The site of the project is about 5,500 hectares sitting about 15 km east of Wyndham. Contact Energy has stated the project would take two and a half years to install and another 12 months for 'site rehabilitation', and that it would have 160-240 jobs during construction and 10-14 jobs once operational.

If the site is built out to the proposed 300MW it would be the largest wind farm in the country ahead of today's largest, the 222MW Turitea Wind Farm. Other proposals for similar or larger wind farms exist, such as the Kaihiku Wind Farm which would also be in the Catlins and is also proposed to be 300MW.

Whether the project goes ahead may be tied to the future of the Tiwai Point Aluminium Smelter. This smelter uses 13% of New Zealand's electricity, and has been considering closing subject to power price negotiations. If it did, Southland would have a large surplus of electricity generation and this could affect the viability of the Southland Wind Farm. However, Contact Energy have also said that power demand in Southland is growing, and if Fonterra's plants were electrified this would consume "quite a significant chunk" of the wind farm's generation.

The project was originally proposed by Wind Prospect CWP (NZ) Ltd in 2008. Wind Prospect's initial proposal was for a 150MW wind farm (50 turbines of 3MW each). The project was purchased by Genesis Energy Limited in June 2010. But by 2011 Genesis said the project was not a priority as the company focused its attention elsewhere, such as a wind farm in Wairarapa. The project had already attracted opposition, such as from the West Catlins Preservation Society which had concerns about the visual impact.

In 2023 the proposal was revived by Contact Energy. It would be Contact's first wind power station. This new version initially proposed 50 turbines, but this was later increased to 55. Contact said that if approved, construction would start in 2025. The project was initially estimated to cost $700 m to $900 m, though by November 2023 this was revised to $1 billion.

The proposal faces opposition by the West Catlins Preservation Society. Members have stated that the project would visually impact the area, and affect the environment and wildlife. They have also questioned the need for more power generation in the province, and suggested that if more power is needed that hydroelectric stations would be preferable. A petition against the project received at least 200 signatures. Part of the wind farm site has been identified as an "outstanding natural landscape" in a report commissioned by four Southland councils in 2018 and finalised in 2019.

In July 2023 the project was accepted for fast-tracking towards resource consent approval under the COVID-19 Recovery (Fast-track Consenting) Act 2020. Contact Energy lodged a resource consent application with the Environmental Protection Authority (EPA) in December 2023. The laws creating the fast-track process have since been repealed but Contact's application was filed in time to use it. The fast-track process gives the decision to an expert consenting panel. The chair of the panel is Clare Leniham, who began as an environmental and public law barrister in 2012 and has over 20 years of experience advising and acting in resource management law, conservation and public law and land law. The EPA will provide advice and administrative support to the panel.

The fast-track process blocks the general public from the resource consent process, and Southland District Council opposed the use of the fast-track process because of this. However, the panel is still required under the law to invite written comments on the application from certain groups. The panel invited people and entities such as the West Catlins Preservation Society, all adjacent landowners, multiple district and regional councils, Te Rūnanga o Ngāi Tahu, and multiple government ministers. Comments were required by 25 July 2024 and were published shortly after that. The EPA has also sought more information from Contact Energy on multiple occasions, such as light spill distances, dwellings near the wind farm, and why Contact did not prepare management plans in consultation with Te Ao Mārama Inc, the iwi liaison entity for Southland's four rūnanga.

In August 2024, after public feedback was published, the consent application was paused at Contact Energy's request. Contact requested the pause so it could address the matters raised "and where necessary, work through issues with commenters". Contact stated it expected the pause "to be a month or so".

• Wind power in New Zealand

Ministry for the Environment - Decision to consider Southland Wind Farm under the fast-track process

Environmental Protection Authority - publications on the resource consent application, including public feedback