The New Zealand Security Intelligence Service (NZSIS or SIS; Māori: Te Pā Whakamarumaru) is New Zealand's primary national intelligence agency. It is responsible for providing information and advising on matters including national security (including counterterrorism and counterintelligence) and foreign intelligence. It is headquartered in Wellington and overseen by a Director-General, the Minister of New Zealand Security Intelligence Service, and the parliamentary intelligence and security committee; independent oversight is provided by the Inspector-General of Intelligence and Security.

SIS was established on 28 November 1956 with the primary function of combating perceived increases in Soviet intelligence operations in Australia and New Zealand. Since then, its legislated powers have expanded to increase its monitoring capabilities and include entry into private property. Its role has also expanded to include countering domestic and international terrorism, chemical, biological, and cyber threats.

The organization has been criticised for its role in numerous high-profile incidents such as the 1974 arrest of Bill Sutch on charges of spying for the Soviet Union, the 1981 assassination attempt by Christopher Lewis on Queen Elizabeth II, and the 1996 invasion of GATT Watchdog organiser Aziz Choudry's home. It has also been criticised for its failures to anticipate or prevent incidents such as the 1985 bombing of the Rainbow Warrior, the 2004 purchasing of New Zealand passports by Israeli "intelligence contract assets", and the 2019 Christchurch Mosque Shootings by an Australian alt-right white supremacist terrorist.