Sydney welcomed 2025 with a massive fireworks display at its iconic harbour.

The self-proclaimed "New Year's capital of the world", sprayed nine tonnes of fireworks from its iconic Opera House and Harbour Bridge at midnight, creating a spectacle that was awash with vibrant colours.

Authorities said more than a million people gathered to watch the display as British pop star Robbie Williams led a singalong while Indigenous ceremonies and performances acknowledged the land's first people.

Earlier, Auckland became the first major city to ring in the new year, with thousands of revellers counting down to 2025 and cheering at colourful fireworks launched from New Zealand’s tallest structure, Sky Tower, and a spectacular downtown light show.

Thousands also thronged to downtown or climbed the city’s ring of volcanic peaks for a fireworks vantage point, and a light display recognising Auckland’s Indigenous tribes.

It follows a year marked by protests over Māori rights in the nation of five million people.

Countries in the South Pacific Ocean are the first to ring in the New Year, with midnight in New Zealand striking 18 hours before the ball drop in Times Square in New York. (Agencies)