The group includes creative and performing artists, authors, scientists and a lawyer.
Actor Neve (nev) Campbell, Booker-prize-winning author Michael Ondaatje (on-DAHCH'-ay) and musician Gord Downie of rock group The Tragically Hip are among those who have signed the letter.
It says that Young's tour raised more than $500,000 to help the Athabasca Chipewyan band pay for a legal attempt to protect its traditional land north of Fort McMurray.
The letter also says that Canada must decide if it wants to support First Nations rights and protect the environment.
Young played in Toronto, Winnipeg, Regina and Calgary, and drew fire from politicians and industry over his comments likening the oilsands to Hiroshima.
"The time has come for Canada to decide if we want a future where First Nations rights and title are honoured, agreements with other countries to protect the climate are honoured, and our laws are not written by powerful oil companies," says the letter released Monday.
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