From New Zealand to New York, millions around the world enjoyed spectacular firework displays to celebrate the arrival of 2020.
Hopes were high for the new year.
But it started with tragedy in Indonesia, where flash floods in the country's capital, Jakarta, and nearby towns have killed 43 people and forced almost 400,000 to flee their homes.
Meanwhile, people were evacuated from New South Wales and Victoria amid the threat of Australia's ongoing wildfires.
Then, on Friday, US-Iran relations were plunged into a new crisis when President Donald Trump authorised a drone strike that killed Iranian military chief Qassem Soleimani.
Here's a look at this week in pictures: