A statement from NBC Universal revealed the move late Friday.
"MSNBC and Keith Olbermann have ended their contract," it read. "The last broadcast of 'Countdown with Keith Olbermann' will be this evening. MSNBC thanks Keith for his integral role in MSNBC's success and we wish him well in his future endeavors."
At the end of his show Friday night, Olbermann announced his departure in typical deadpan style, evoking scenes from the film "Network" and thanking viewers for keeping him on the air for eight years.
"In the mundane world of television goodbyes, reality is laughably uncooperative," Olbermann said before launching into a story about his exit from ESPN 13 years ago.
"As God as my witness, in the commercial break just before the emotional moment, the producer got into my earpiece and he said, 'um, can you cut it down to 15 seconds so we get in this tennis result from Stuttgart,'" he said, half-smiling, pausing for composure.
"So I'm grateful I have a little more time to sign off here. Regardless, this is the last edition of Countdown."
Olbermann thanked his crew and co-workers, with special praise for the man he called "my greatest protector and most indefatigable cheerleader," Tim Russert, the host of NBC's "Meet the Press" who died in 2008.
Olbermann was suspended for two days in November after the news website Politico revealed donations made to three Democrats seeking federal office. One of them was U.S. Rep. Gabrielle Giffords, who was wounded earlier this month in a mass shooting in Tucson, Arizona.
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