"The Vancouver Canucks had success under Mike's leadership, and we nearly reached our ultimate goal; but I believe we have reached a point where a change in leadership and new voice is needed," chairman of Canucks Sports and Entertainment Francesco Aquilini said in a statement.
Gillis was hired in 2008, replacing Dave Nonis.
Gillis was arguably the most successful GM in club history but has increasingly come under fire in the past year or two for several moves, but those involving goaltending and coaching hold the greatest sway.
Goalie Roberto Luongo, who helped lead the Canucks to the Stanley Cup final in 2011, was the subject of trade rumours after the following season when he was benched by coach Alain Vigneault for a playoff game in favour of Cory Schneider.
The Canucks couldn't move Luongo, largely because of the marathon contract Gillis struck with the netminder through 2021-22.
In the summer of 2013, after a first round exit, Vigneault was fired and Schneider traded to the Devils. The latter move surprised many hockey observers and required much fence-mending with Luongo, who went from on his way out to re-inserted as the No. 1 man in net.
But Vancouver swooned at the midway point of this season, with Luongo dealt ahead of the deadline to Florida.
The Canucks thus went from perhaps the top goalie tandem in the league to a duo of relatively unproven Eddie Lack and Jacob Markstrom in a span of a year.
Vancouver's struggles this year have come with John Tortorella behind the bench.
The decision to hire the abrasive Tortorella, whose previous teams played a style not consistent with the Canucks of recent years, was also questioned.
Tortorella didn't help matters by incurring a lengthy suspension after a testy game between the Canucks and Flames.