Dunedin's March for Science - held on the Museum Reserve - was one of the first of more than 500 such marches and rallies worldwide on Earth Day.
The March for Science movement has been launched by scientists and others critical of the agenda of United States President Donald Trump's administration.
About 300 people gathered on the reserve at the peak of Dunedin's event and listened to speakers including Sir Alan Mark, Ian Griffin and Dunedin-based MPs David Clark and Metiria Turei.
Otago Museum science communicator Amadeo Enriquez-Ballestero also wowed the crowd with science demonstrations.
Dunedin organiser Cindy Hall said she was pleased with the turnout.
''We are really, really happy, especially given it's the school holidays and it's the university break,'' she said.
''Our aim was for it to be a celebration because there's so much here in terms of intellectual pursuits.
''It was so positive and there were lots of kids there engaged and really, really excited.
''We just wanted people to come together, be together, speak to each other and, maybe, learn something.''
Dunedin Mayor Dave Cull told the crowd of the importance of science to the city and the world, especially considering the challenges the planet faced at present.
''Every generation has its flat-earthers,'' he said. ''Our cross to bear is climate-change deniers.
''There are decisions to be made and as a city if we want to make sound, evidence-based decisions we need to see our future through the lens of good science.''
