WASHINGTON — Interior Secretary Ryan Zinke, who has been the subject of more than a dozen government investigations, will leave his position by the end of the year, President Trump said Saturday, adding to the list of top officials to exit from the administration.

Mr. Trump announced Mr. Zinke’s departure via Twitter, saying that the secretary “has accomplished much during his tenure, and I want to thank him for his service to our Nation.”

He added that a new interior secretary would be named next week.

White House officials have long been concerned about the allegations against Mr. Zinke, according to one person who has been involved in the discussions. In recent months, it became apparent that he would be a target for Democratic oversight when the party assumes control of the House in the new year, this person said.

Mr. Zinke said Saturday that he chose to resign because he thought the many investigations of him would undermine the president and his administration.