Park staff across London are being trained to spot and respond to harassment, as part of a new drive to make green spaces safer for women and girls.
The training, developed by the Suzy Lamplugh Trust and the University of Leeds, will give staff the tools to step in when they see inappropriate behaviour. Members of the public can also sign up for the course.
Campaigners say many women avoid parks, especially after dark, due to safety concerns.
The charity which campaigns against stalking and harassment is also calling for better lighting, more staff, and for women to have a say in how parks are designed.
"The kinds of behaviours this training would assist with include inappropriate comments, gestures, cat calling or even unwanted touching," said Saskia Garner from the Suzy Lamplugh Trust.
"Someone sitting down next to you on a bench and putting their arm around you – anything that makes you feel unsafe is not OK."
Ms Garner added that many people want to help but are unsure how to act safely.
"You wouldn't go in a park by yourself after dark or even with one other person because it doesn't feel safe," one woman told BBC London in the Regent's Park.
Another added: "[Parks aren't] not very well lit… in the one where I live there are no street lamps."
The Suzy Lamplugh Trust, set up after the 1986 disappearance of estate agent Suzy Lamplugh, works to reduce violence and harassment through training and support.
"People don't feel they can intervene," Ms Garner said.
"They worry about making things worse. The women we spoke to said they didn't feel safe to challenge the harassment and didn't think anyone would help them."
