Olbermann thanked his fans during his sudden and brief farewell: "My gratitude to you in boundless," he said. "This may the only television program where in the host was much more in awe of the audience than vice versa. You will always be in my heart for that."
Following his announcement, MSNBC sent out the following statement: "MSNBC and Keith Olbermann have ended their contract. 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."
The Last Word with Lawrence O'Donnell will replace Countdown at 8/7c, while The Ed Show moves to 10/9c.
In November, Olbermann was suspended for five days by network president Phil Griffin following a report that the Countdown host made multiple campaign contributions before the election.
In 2008, MSNBC signed Olbermann to a four-year contract extension worth an estimated $30 million, which would have seen him continue through the next presidential election.
Watch Olbermann's exit on Countdown here: