The Gore-tex Scottish National Trail starts where the Pennine Way ends at Kirk Yetholm in the Borders, wends through hills to the central belt where it follows the Forth and Clyde and Union canals between Edinburgh and Glasgow, before striking north through Highland Perthshire and on to the Highlands.
It includes sections of several existing, shorter trails, including St Cuthbert's Way, the Rob Roy Way and the Cape Wrath Trail.
Writer and TV presenter Cameron McNeish, editor-at-large of TGO magazine, who had the idea for the route, said: "I wanted to re-discover my country for myself, especially those areas I wasn't so familiar with, and in doing so walked a route I believe can stand comparison with the best routes anywhere in the world."
Launching the route at the Water of Leith Visitor Centre in Edinburgh, First Minister Alex Salmond said: "It showcases this beautiful country of ours, reminding us of Scotland's history and beauty and highlighting the rich variety of our national landscape."
He added that it would add to Scotland's already excellent reputation as a tourist destination.
Initially, it will have signs at the beginning, at the Water of Leith Visitor Centre and at the end, but Mr McNeish, right, hopes more will be added.
A guidebook to the route, Scotland End to End, is available and a two-part BBC Two Scotland programme about the trail is due to be screened at Christmas.
David Thomson, convener of Ramblers Scotland, said it would encourage enjoyment of the outdoors but added that new path networks were needed in many parts of Scotland and the Scottish Government needed to spend more than 10% of its transport budget on walking and cycling routes, not the current 1%.