The pair have been added to the bill of Fringe by the Sea, North Berwick’s annual cultural celebration, which is due to be staged across 10 days in August in the East Lothian town.
The appearances of the two Edinburgh-born stars are expected to be among the highlights of the literary strand of the festival, which is planned to be staged in venues across North Berwick for the first time as part of a “Covid-secure” plan to bring the event back this summer.
Pop-up marquees and “stretch tents” with capacities of up to 500 will play host to shows from 6-15 August.
Organisers today revealed that broadcaster Paul Murton, present of the BBC show Grand Tours of Scotland, travel and medical writer Gavin Francis, and novelist Helen McClory will be part of the line-up.
The event, which is hope to bring attract around 20,000 festivalgoers from 6-15 August, will also feature live music and comedy, as well as showcases for food and drink producers and craft-makers.
Award-winning Scots comic Janey Godley, American disco legend Candi Staton, electronica outfit Basement Jaxx, Fun Lovin’ Criminals frontman Huey Morgan, Hebridean rockers Peat & Diesel and Scottish folk favourites The Poozies will all be staging headline shows.
Porter is expected to discuss her career and her battles with depression, anorexia, self-harming and homelessness, which were the subject of an award-winning BBC Scotland documentary last year.
She said: “I am beyond excited to come to this year’s Fringe by the Sea festival.
"Having spent lockdown in my hometown of London throughout the pandemic, I’m desperate to return to Scotland to see some friendly faces and green spaces.
“I look forward to sharing my personal story with people coming to this year’s event. So many of us have struggled with our mental health during the pandemic, so it’s important to talk about it and support each other. Then shake it off on the dance floor with the mighty
Basement Jaxx later that night.”
Welsh will be appearing at Fringe by the Sea 25 years after the release of the film adaptation of the novel Trainspotting and months after the launch of Creation Stories, the new movie he wrote based on the life of Scottish music mogul Alan McGee.
He said: "The prospect of a live event with an audience is a joyful one, and North Berwick is top draw as a location for it.
“There's plenty to chat about and I'm looking forward to having some fun with the good people at Fringe by the Sea."
Francis, a GP who splits his time between Edinburgh and Orkney, will discuss Intensive Care, his new book about the impact of the pandemic on urban and rural communities.
Edinburgh-based author McClory, a former Saltire First Book of the Year winner, will be discussing her brand new novel Bitterhall.
Murton’s fans will hear from discuss The Highlands, his new book which will see him cast a fresh eye on iconic destinations such as Glencoe, Ben Nevis, Loch Ness and the Cairngorms.