The 84-year-old, who has written, designed and illustrated seven novels to date, was named the inaugural recipient of the Saltire Society’s prize at its annual awards ceremony in Edinburgh.
However Gray, who missed the evemt at the National Museum of Scotland due to illness, admitted it was unlikely he would ever write another novel or play.
The Saltire Literature Awards ceremony also saw a Strathclyde University professor, Kirstie Blair, win the main Scottish Book of the Year title for her study of working-class poetry in Victorian Scotland.
Previours winners of the prestigious title include Edwin Morgan, Tom Leonard, Norman MacCaig, William McIlvanney, Liz Lochhead and Janice Galloway.
Gray was born in Glasgow in 1934 and studied and later taught at the city’s art school.
Lanark, which was finally published in 1981, won him the Saltire Scottish Book of the Year title.
Gray, who won the same award in 2011 with his autobiographical book A Life In Pictures, also wrote plays for television, radio and the stage and has been a prolific painter. Some of his best known work in Glasgow was created for the Hillhead underground and the Oran Mor arts centre.
Gray was honoured with a major exhibition of around 100 works at Glasgow’s Kelvingrove Art Gallery and Museum in 2014 to mark his 80th birthday.
However, he has been unable to walk since seriously injuring himself in a fall in 2015 – weeks before an adaptation of Lanark was due to be staged at the Edinburgh International Festival.
The Saltire Society, which has been staging the nation’s most prestigious literary awards since 1937, created the new lifetime achievement honour to recognise an individual who has made “a meaningful creative contribution to the world of literature”.
A shortlist was drawn up based on nominations by society trustees and the awards judges for its other awards.
The judging panel said: “For more than 40 years, Alasdair Gray’s plentiful and diverse work has influenced writers and the literary scene worldwide.
"Alasdair has never been one to be confined by genre and has freed up form for many writers and artists.
"To say he is influential is an understatement. He has inspired generations and will continue to do so for many years to come.”
Sarah Mason, programme director of the Saltire Society, said: “Alasdair Gray’s influence runs deep within Scotland and much further afield. We are delighted to be able to recognise his contribution in this way.”
In a message read out at the ceremony, Gray said: “At the end of next month I will be 85 years old.
"I think it unlikely that I will write another work of fiction or play, and though I still have several paintings to complete, I doubt if I will sell many more. For this reason I am very grateful for the Saltire Society’s gift.”
Blair’s Scottish Book of the Year winner showcased the work of more than 50 working-class poets in Victorian Scotland, most of whom had never previously been recognised, and is said to present fresh evidence of “an active, lively, and political culture of local writing”.
The judges said: “The fact that it is an important, significant piece of research did not discolour its enjoyability, with laugh out loud moments and fascinating facts. The judges felt a warmth from it and to it.”
The best “first book” award was shared between two authors – Stephen Rutt for his celebration of seabirds, The Seafarers, and Clare Hunter for Threads Of Life, which charted the history of sewing and embroidery.
Wick-born author Ewan Morrison won the best fiction book title for Nina X.