Ms MacDonald, 70, represented the Scottish National Party at both Westminster and Holyrood, before latterly serving as an Independent MSP.
Her husband, former SNP deputy leader Jim Sillars, who was at her bedside when she died, said: "She supported and inspired generations of idealists and campaigners who, like her, wanted Scotland to take its place in the world.
"Her talent acted like a magnet and she gave her time so freely to so many for so long."
Among the many tributes, Holyrood Presiding Officer Tricia Marwick said: "To be known and recognised by a first name is reserved to very few. But everyone knew Margo. She had a rare skill in being able to translate political speak into language we could all understand."
Picture: Gordon Terris