This Sunday's Brisbane International Women's Day Fun Run, presented by Queensland X-Ray has been cancelled due to the potential impact of Tropical Cyclone Alfred.
Mater Foundation Chief Executive Andrew Thomas said the decision was taken to ensure the safety of participants, staff, volunteers and the wider community.
More than 23,000 people were due to take part in the Brisbane fun run, which raises vital funds to support women with breast cancer.
"Due to the upcoming weather event, we have regrettably decided to cancel the International Women's Day Fun Run in Brisbane on Sunday 9 March," Mr Thomas said.
"The safety of everyone involved in this event is Mater's absolute priority. This decision has not been taken lightly and has been made following close consultation with local and state government, as well as event stakeholders"
Fun runners in South East Queensland will be able to continue the fight against breast cancer until Sunday 23 March.
"We are deeply disappointed that the Sea of Pink won't be able to come together in Brisbane to support this important cause," Mr Thomas said.
"Participants will still be able to turn their local streets and parks pink by participating in our virtual event – 5K Your Way – which has been extended until Sunday 23 March, once Tropical Cyclone Alfred is well and truly behind us.
"Wherever and whenever our supporters run, Mater Foundation expects this year's event will still raise more than $1.8 million to fight breast cancer.
"On behalf of every patient fighting breast cancer, and Mater's dedicated staff and researchers, we thank Queenslanders for their incredible support."
Sunday's Springfield International Women's Day Fun Run at Brighton Homes Arena has also been postponed.
Mr Thomas said the Townsville International Women's Day Fun Run, due to take place on Saturday 8 March at Cluden Park, will go ahead as planned.
Local 5K Your Way fun runs in Central and North Queensland are also expected to proceed.
