Starting in Wagga in honour of 12-year-old Lauren Rafferty, who lost her life to suicide in May of last year, Sebastian will complete the trek alongside best friend Tim Freeburn.

The pair will walk from Wagga to Goulburn on the state's Southern Tablelands; Mittagong to Casula in southern Sydney; before arriving in Sydney's CBD.

Sebastian is inviting residents to walk the first kilometre of the trek, starting at Wagga Riverside at 6am on Friday, July 1.

The trek is part of the Sebastian Foundation's Step Change for mental health which aims to raise awareness around youth suicides, while also raising funds for the Open Parachute program.

Open Parachute is a program founded by Dr Hayley Watson that focuses on building psychological skills in school-aged children to help them address life's challenges, ultimately preventing youth suicides.

"We are aiming high, we hope to raise $1 million which will put 35,000 kids through Open Parachute," Sebastian said.

So far the pair have already raised more than $650,380.

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Open Parachute is a program that is close to Sebastian's heart as he, alongside his wife Julie, is a prominent advocate for mental health awareness.

"This will give young people the best possible chance to grow up healthy and happy, as well as a skill set which helps them navigate challenges in their lives," Sebastian said.

To make a donation visit sebastian.grassrootz.com/step-change.