He had been been in hospital recovering from a viral infection when he suffered a heart attack last night.
Wyllie's death comes in a year when a series of events had been arranged to mark his 90th birthday and a remarkably colourful and diverse canon.
Neil Baxter, a close friend and collaborator, said today: "George was an artist of real importance, not just in Scottish but in international terms."
The artist and writer, a resident of Gourock for over 50 years, was best known for his Straw Locomotive and Paper Boat "social sculptures".
He famously described himself as a scul?tor because he claimed that the question mark was too important to be left to the end.
Just last week, it was announced that his work was set to inspire a new generation, thanks to a major £158,510.00 award from the Year of Creative Scotland, 2012 and its First in a Lifetime Creative Experiences initiative.
Louise Wyllie, his elder daughter, said: "My father was delighted at all the developments which the Friends of George Wyllie have made in the last year in establishing his legacy and he was keen to know what was happening right up to the end.
"He was delighted about the latest news which will see us putting his life and work into the curriculum in Scottish schools and working with skilled shipyard workers in Inverclyde on the creation of giant question marks.
"He was so pleased with the idea of The Whysman Festival which is running throughout 2012 to celebrate his artistic legacy and just a couple of months ago he attended a small pre-opening party for the festival at The Collins Gallery for his archive exhibition, A Life Less Ordinary, I am so glad now that he saw the start of what is a year of celebration.
"He really did live a life less ordinary. There was no-one else like him and I suspect there never will be."
Arts writer Jan Patience, chair of the Friends of George Wyllie said: "George Wyllie was a remarkable artist who reached out beyond the confines of the art gallery scene and connected with real people all over the world through his thought-provoking art.
"He had the knack of making you ask questions, of not accepting the status quo. His mind was constantly enquiring, and his art was constantly pushing out barriers. That is his legacy."
George Ralston Wyllie was born in Shettleston, Glasgow on Hogmanay, 1921. He was known to his family and friends as Ralston, until he decided to become an artist in his late 40s. In his artist persona, he was George, but to close family and friends, he was still Ralston.
Wyllie and his younger brother Banks, grew up in the Craigton area of Glasgow, where their parents, Andrew and Harriet, moved when Wyllie was a little boy, The brothers were brought up in the shadow of the shipyards. Wyllie later described himself as being "disadvantaged by a happy childhood".
His first job was an office boy in a shipping company in Govan. He then trained as an engineer with the Post Office before joining the Royal Navy at the beginning of the second world war.
During active service, Wyllie visited Hiroshima in the aftermath of the dropping of an atomic bomb on the Japanese city. The experience was to have a profound effect on his life, and later on his work as an artist.
Wyllie's self-proclaimed status as "the best bogie-builder in Cardonald" as well as a burgeoning musical and dancing talent hinted at an early creativity.
After the war, and marriage to his beloved Daphne, he worked as a customs and excise officer in Glasgow, Prestwick, and Ireland before settling in Gourock, where his two daughters, Louise and Elaine, were brought up.
Although it had always been in the background, he decided it was time for art in 1965, and he attended a local college in Greenock to learn how to weld. Once of the first ever pieces of artwork he sold was to Ferguson's shipyard in Greenock.
He left the customs service in 1979 at the age of 58 and entered into a four-decade long late-flowering career as an artist.
In the 1980s, through the late Barbara Grigor, a champion of many a Scottish artist, Wyllie met the American kinetic artist, George Rickey, who invited him to work with him in America.
He later described this experience as a great art release. He was also hugely influenced by the German artist, Joseph Beuys, after meeting him through Edinburgh gallery owner, Richard Demarco.
Wyllie's award-winning play about the iniquities of the world banking system, A Day Down a Goldmine, was produced several times throughout the 1980s. The two-handed play featured Wyllie as a character called His Assistant (Goldbunnet) alongside acclaimed actors such as Russell Hunter and Bill Paterson.
In 1987, he attracted international attention with his Straw Locomotive, which hung from the Finnieston crane in Glasgow before being burned in nearby Springburn in a Viking Style funeral.
Two years later, his Paper Boat was seen by millions as it sailed around the world from Glasgow to New York and back to Scotland. It even made it onto the front page of the Wall Street Journal when it berthed at the World Financial Center in New York in 1990.
Wyllie's daughters Louise Wyllie and Elaine Aitken, set up The Friends of George Wyllie, after their father went into a care home in Greenock in 2011.
Friends, or "Chums" of George include his old friends, artists Dawson and Liz Murray, Neil Baxter, of the Scottish architecture body, the RIAS and filmmaker, Murray Grigor, whose award-winning film 1990 film about Wyllie, The Why?s Man, has recently been re-released on DVD.
George Wyllie was predeceased by his wife Daphne, who died in 2004. He is survived by daughters Louise Wyllie and Elaine Aitken, as well as grandsons, Calvin and Lewis, and grand-daughter, Jennifer.