"I have relieved Matt Millen of his duties effective immediately," Lions owner William Clay Ford said in a statement Wednesday afternoon.
Millen's teams won a league-low 31 games since he took over in 2001, but Ford refused to get rid of him until now.
Bill Ford Jr., son of the team owner, said Monday he would fire Millen if he had the authority.
Detroit was routed in each of its first three games this season, falling behind 21-0 twice and 21-3 once en route to lopsided losses. The Lions are off this week.
The 0-3 start dropped Millen to 31-84 overall, giving the Lions at least 10 more losses than any other NFL team the past seven-plus seasons during one of the worst stretches in league history.
NFC North blog
Firing Matt Millen will only matter for the Lions if they find the right replacement to rebuild the franchise, ESPN.com's Kevin Seifert writes. Blog
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FoxSports.com was the first to report Millen's departure.
"I am very disappointed with where we are as a team after our start this season," William Clay Ford added in his statement. "Our sole focus now is preparing for our next game against Chicago."
The front office will be led by executive vice president Tom Lewand, who will report to the owner on business issues. Assistant general manager Martin Mayhew was promoted to general manager, and will report to the owner on football matters.
"These decisions are for the duration of the 2008 season," Ford's statement said. "Once the season is over, we will undergo a thorough and comprehensive evaluation of our entire football operation and put together a plan that we believe will transform this team into a winner."
The tipping point might have been public comments made by the owner's son. Bill Ford Jr., who is the Lions' vice chairman as well as Ford Motor Co. executive chairman, said that Millen should leave the team.
"I think the fans deserve better," Bill Ford told reporters on Monday. "And if it were in my authority, which it's not, I'd make some significant changes."
His father finally agreed that Millen had to go.
Millen was spotted amid large packing boxes Wednesday morning. There was no word on what happens with the rest of Millen's contract; he had an extension that ran through 2010, worth $5 million a year.
"We're fine," Millen's wife, Patty, told ESPN senior NFL analyst Chris Mortensen. "In the world's view, this may look like failure. It's been a hard road, footballwise, but we've gotten a lot of eternal blessings. We'll move forward. I told him, 'You're out of football prison now' and we have a greater purpose."
Drivers of vehicles whizzing past the Allen Park facility beeped their horns and gleefully yelled out about the end of the Millen era. A gaggle of reporters, videographers and still photographers roamed around the grounds.
Eddie Gates drove through the team's parking lot in his minivan as his girlfriend, Sue Stanton, held a sign, "Millen Must Go To Get a Super Bowl," out the window.
"I've been a season-ticket holder for 28 years and because they fired Matt Millen, I'm going to renew," Gates said. "This is the happiest day of my life."
The Fords -- father and son -- had been thrilled when they lured Millen out of the broadcast booth to run their hapless franchise.
"I'm willing to stake my reputation on Matt's success," Bill Ford said after Millen was introduced at a news conference in January 2001.
Millen was the team's first general manager since Russ Thomas left in 1989. The Lions allowed their coaches -- Wayne Fontes, Bobby Ross and Gary Moeller -- to run the football operation after Thomas resigned.
"We've been pretty much stuck on dead center for quite a few years," William Clay Ford said when Millen was hired. "Matt offers us an opportunity to move ahead."
Rod Marinelli will be left with the task of salvaging something from the final 13 games of the season. But he and the players haven't inspired much confidence, with an NFC-worst 10-25 record since 2006.
Ultimately, the Lions are left with Millen's mess that led to a pitiful era that compares only to Tampa Bay's 12 straight double-digit loss seasons from 1983 to 1994.
This offseason was productive and the practices were great, Millen and Marinelli insisted, but that didn't make a difference on Sundays this season.
The Lions are winless, and 1-10 dating to last season. The latest loss at San Francisco dropped Marinelli to 3-15 on the road and dropped the Lions to 8-60 as visitors with Millen in charge.
The former Penn State standout was an NFL linebacker from 1980 to 1991 with the Raiders, San Francisco 49ers and Washington Redskins. He went to the Super Bowl four times.
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