The Hibs fan opened the registration for the virtual challenge which asks competitors to walk the equivalent of 12,106,000 steps from Scotland to the south Indian city.
Trainspotting author Welsh, a long-term ambassador for Scottish charity Scottish Love in Action, walked the first mile of the 5,000 miles between Scotland and Hyderabad on Monday.
The charity, which helps the poorest children in India, is raising cash through its Girls’ Lives Matter appeal.
Welsh opened registration for the fundraiser at Edinburgh Castle Esplanade with a small group of participants before setting off down the Royal Mile.
The charity wants help to virtually walk the 5,000 miles/8,000km, from Scotland to Hyderabad during June 2017.
Participants can walk, run or cycle a minimum of 10km, which will contribute towards the equivalent distance between the countries.
SLA provides funding to three grassroots non-governmental organisations (NGOs) which run projects in the south east Indian states of Andhra Pradesh and Telangana.
Numerous children it helps are orphans and have been forced to beg and live on the streets.
Founder and chairwoman Gillie Davidson said: “Many of the children we care for have only managed to survive by scavenging in rubbish tips, or living on the streets where they are open to being trafficked into prostitution or forced labour.
“All the money we raise from challenges like Hoof it to Hyderabad give these children a chance in life and we’d like to thank everyone for this support.”
To register for the challenge visit www.sla-india.org.