Lauer was one of the highest paid news anchors in the world - and in March it was revealed he paid $13m for a high country station in New Zealand's South Island on the shore of Lake Hawea.
Lauer is one of many whose careers have been hit by harassment allegations in the weeks since Hollywood mogul Harvey Weinstein was accused by numerous women of sexual assault. Last week, Lauer's morning rival on CBS, Charlie Rose, was fired after eight women told the Washington Post that he had acted inappropriately toward them over a number of years.
The post-Weinstein wave has brought down figures in the news, entertainment and political fields, and renewed discussion about allegations against President Donald Trump first raised when he was the Republican candidate for the office last year.
The news of Lauer's firing prompted an early-morning tweet from Trump: "Wow, Matt Lauer was just fired from NBC for 'inappropriate sexual behavior in the workplace'," he wrote. "But when will the top executives at NBC & Comcast be fired for putting out so much Fake News. Check out Andy Lack's past!"
Trump was the star of the long-running NBC reality programmes The Apprentice and Celebrity Apprentice before announcing his entry into politics in 2015. During his tenure on the programmes, cast and crew members said he made inappropriate comments to women. Contestant Summer Zervos has sued him for defamation for his comments stemming from her allegation that he harassed her during production.
The Today staff broke the news about Lauer, marking one of the few instances in which a news organisation was first to report on the misconduct of one of its own employees.
"All we can say is we are heartbroken," said Guthrie, who appeared to be near tears when she disclosed Lauer's firing. "I'm heartbroken. How do you reconcile your love for someone with the revelation that they have behaved badly?"
She said she was "heartbroken for the brave colleague who came forward to tell her story". Lauer's accuser has not been identified.
After making the announcement, Guthrie turned to co-host Hoda Kotb, who was filling in for Lauer, and grabbed her hand in a gesture of solidarity and support.
Weather forecaster Al Roker, who was also clearly moved by the announcement, told viewers, "I'm still trying to process the news."
In his staff memo, Lack wrote, "Our highest priority is to create a workplace environment where everyone feels safe and protected, and to ensure that any actions that run counter to our core values are met with consequences, no matter who the offender.
"We are deeply saddened by this turn of events. But we will face it together as a news organisation - and do it in as transparent a manner as we can."
NBC did not announce who would replace Lauer on Today, the daily, four-hour news and discussion programme that is the network's most famous and most profitable news show.
In addition to Lauer and Rose, prominent TV news figures who've been fired for alleged harassment include Bill O'Reilly and Roger Ailes of Fox News and political commentator Mark Halperin, who served as an analyst for NBC News and MSNBC.
Trump weighed in with another tweet later in the morning, this time targeting MSNBC president Phil Griffin and Morning Joe host Joe Scarborough: "So now that Matt Lauer is gone when will the Fake News practitioners at NBC be terminating the contract of Phil Griffin? And will they terminate low ratings Joe Scarborough based on the 'unsolved mystery' that took place in Florida years ago. Investigate!"
Trump was apparently referring to the death of an intern in Scarborough's district office in Florida in 1999 when Scarborough was a congressman. According to a news report in the St Petersburg Times in 2001, a medical examiner determined that she died after she lost consciousness because of a heart problem, fell and hit her head on a desk. There was no evidence of foul play.
Lauer has been as much the face of Today as anyone in its 66 years on the air, a star commanding a reported $25 million-per-year salary.
As co-host he has interviewed hundreds of celebrities, politicians and other newsmakers. His interviews of presidential candidates Trump and Hillary Clinton in September last year drew widespread criticism, particularly his questioning of Clinton about issues surrounding her private email server and his failure to challenge Trump on his claims of opposition to the war in Iraq in 2003.
Lauer also conducted the only TV interview with NBC anchor Brian Williams in 2015 after Williams returned to NBC after a six-month suspension over allegations he had exaggerated his reporting exploits.
Lauer's signature segment, running from 1998 until 2009, was an annual trek to various exotic locales, billed as " Where in the World is Matt Lauer?"
He also popped up on other NBC programmes, such as co-hosting the network's coverage of the Macy's Thanksgiving Day Parade and the opening ceremonies of several Olympic Games. He substituted for Bob Costas, NBC's primary host during the 2014 Winter Olympics when Costas developed an eye infection.
Lauer's two-year contract was set to expire at the end of 2018
