She had been filling in for Lauer since he was sacked, and for at least three weeks without him, the show beat rival "Good Morning America" in ratings, The New York Times reported.
The vibe is far more celebratory today - see the happy posts below. When Guthrie announced the following morning that Lauer had been dismissed, Kotb was by her side.
Kotb and Guthrie, who has co-anchored TODAY since 2012, will be the first pair of women to anchor TODAY, although they are not the first all-female morning show duo.
Ratings for Today, the longtime former morning-news champ that has been trailing ABC's Good Morning America for the past couple of years, have rebounded strongly in recent weeks after the swift dismissal of Lauer. Kotb has co-hosted the fourth hour of "Today" with Gifford since 2008.
Flood Warning For Clare As Storm Eleanor Approaches
The orange alert is in place for Leinster, Munster and Galway, with a status yellow alert for the rest of the country. Tuesday night will continue windy with strong southwest to west winds, reaching gale force along western coasts.
Kotb told Guthrie there is no one she would rather be co-hosting with in 2018.
Her obvious chemistry with Guthrie has helped navigate the show through the most hard period in its 67-year-history.
Guthrie and Kotb will co-anchor the 7-9 a.m. hours of the show, along with weather anchor Al Roker and Orange Room host Carson Daly.
Kotb officially started in her new role Tuesday. She also hosts a program on Sirius XM satellite radio. On top of all that, we've been lucky enough to watch and delight in her joy as she has built her own family, all while becoming the center of TODAY's.
Kotb joined NBC News in 1998 as a correspondent for "Dateline".