Hoda Kotb, whose megawatt smile and convivial presence have greeted groggy-eyed viewers of NBC’s “Today” show for the past 17 years, said on Thursday that she would step down from her hosting duties early next year.

Her surprise decision, Ms. Kotb said, came after a period of reflection prompted by her recent 60th birthday.

“I just thought the universe was speaking to me,” she said in an interview with The New York Times before she broke the news on-air to “Today” viewers. “This is a time in life for looking inside you, and figuring out what your yearnings are, your callings — where or what direction you’re headed during this new decade.”

A onetime local news reporter, Ms. Kotb (pronounced COT-bee) used an easy intimacy with viewers — not to mention a habit of sipping wine on-air — to transform herself into one of the most famous faces of an entire network, which she joined in 1998 as a “Dateline” correspondent.

Ms. Kotb will remain an occasional contributor to NBC, and she indicated that she might pursue projects in the wellness space (“It’s such a beautiful, fertile, wonderful place to be”). But, she told The Times, “it felt like the time to turn the page on what has been a dream book, a dream quarter-century.”

Her exit will create vacancies in two of the most coveted seats in television news. Ms. Kotb holds both an anchor chair for the flagship “Today” telecast, from 7 to 9 a.m., and a hosting position for its fourth hour at 10 a.m. The “Today” franchise remains a crucial driver of revenue for NBC.