Rachel Maddow, MSNBC’s No. 1 star, is taking a hiatus.

Rachel Maddow, the top-rated anchor on MSNBC and one of the most influential figures in liberal media, is set to take a hiatus from her nightly cable program, according to two people at the network with knowledge of her plans.

Her break is expected to last several weeks, and no return date has been specified, the people said, requesting anonymity to describe private discussions. She is expected to address her viewers on Monday and to begin her leave after Thursday’s broadcast.

It is hard to overstate the importance of Ms. Maddow to the MSNBC brand. Her 9 p.m. show is a beloved destination for liberal viewers, and it is routinely the only prime-time program in cable news that comes close to Fox News’s ratings.

Ms. Maddow was widely expected to take time away from her show this year to pursue other projects, although many in the industry had predicted her break would happen in the spring.

Whether she returns to a full slate of nightly broadcasts, or dials back her schedule to something less grueling, has been the subject of speculation among some MSNBC anchors and producers. The network declined to comment ahead of Ms. Maddow’s broadcast on Monday.

Ms. Maddow will not be entirely absent: She is expected to make occasional return appearances on MSNBC throughout her hiatus, including for the network’s coverage of President Biden’s state of the union speech in March. For now, a rotation of fill-in anchors will handle the network’s 9 p.m. slot.

Ms. Maddow’s new contract with the network, signed last year, allows for her to focus on a variety of efforts beyond her nightly show. Her decision to take a temporary break was reported earlier by Insider.

One of the projects she will work on during the break is a podcast produced for NBCUniversal, one of the people said. She is also working with the actor Ben Stiller on a film adapted from “Bag Man,” a podcast she hosted about the 1970s scandal involving Spiro T. Agnew, who resigned as Richard Nixon’s vice president.

Executives at MSNBC are reconfiguring a schedule in flux. Brian Williams, once the popular 11 p.m. host on MSNBC, left the network late last year. MSNBC said last week that he would be replaced by the anchor Stephanie Ruhle, with “Morning Joe,” the network’s morning franchise, adding an additional hour at 9 a.m.