Katie Couric will fill in as co-anchor on NBC's 'Today' show in January

Katie Couric is returning to NBC's "Today" show for a weeklong fill-in stint at the morning program's anchor desk next month.

Couric will be back alongside Matt Lauer for the week of Jan. 2, according to people at the morning program who are familiar with the plan but not authorized to discuss it publicly.

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Couric will be substituting for Lauer's current on-air partner, Savannah Guthrie, who is on maternity leave after giving birth to her second child Dec. 9. Guthrie recently signed a new long-term contract with "Today."

Couric was co-anchor of "Today" from 1991 to 2006, during which time she became the most popular personality in TV news. She left the program to join CBS, where she become the first solo female anchor of a network evening newscast.

Since 2014, Couric has been global anchor for Yahoo News. She recently produced "Under the Gun," a documentary about gun violence in the U.S.

Couric has returned to "Today" as a guest in the years since she left the program, but she has never filled in as a co-anchor. She did spend a week as a guest co-host of "Today" rival "Good Morning America" in April 2012.

"Today" has been closing the gap with ABC's "Good Morning America" in the ratings race. The NBC program has won three of the last six weeks in overall viewers. "Today" is the leader among viewers in the 25-54 age group important to advertisers that buy time on news programs.