Current Knicks assistant Mike Miller will replace Fizdale on an interim basis.
Knicks president of basketball operations Steve Mills had reportedly started to lay the groundwork that would eventually lead to Fizdale's firing by mid-November.
Friday's news comes just hours after Fizdale led the team's morning practice and said he wasn't concerned about whether he'd be dismissed.
"I don't think about that stuff," the 45-year-old told reporters this afternoon, according to The Athletic's Mike Vorkunov. "I don't think about it at all."
Fizdale's tenure in the Big Apple ends partway through his second season with the club. He leaves with a 21-83 record that gives him a .202 winning percentage - the lowest of any coach in Knicks history, according to The New York Times' Marc Stein. It's also the fifth-worst winning percentage any head coach has posted with a single NBA team in a minimum of 100 games, according to Hoopshype.
Prior to joining the Knicks, Fizdale was a longtime assistant of Miami Heat head coach Eric Spoelstra, winning a pair of titles with the club during its Big Three era.
He was hired as head coach of the Memphis Grizzlies ahead of the 2016-17 campaign but was relieved of his duties in a similar fashion just 19 games into his second season.
Since Pat Riley's resignation in 1995, Jeff Van Gundy and Mike D'Antoni are the only two Knicks head coaches to have lasted at least three full seasons, according to NBC Sports' Tom Haberstroh. The club's next bench boss will be its 13th in the last 18 years.
New York is coming off two consecutive 37-plus-point defeats and has lost eight straight overall.
The Knicks currently own the NBA's second-worst record at 4-18 and are on track for a sixth straight 50-loss season.