Her announcement will come at a news conference scheduled for 11 a.m. at City Hall, where she'll be handling paperwork for her reelection campaign.
Harris, a Democrat, served two terms as San Francisco's district attorney before winning a tight race in 2010 to become California's first female and and first nonwhite attorney general.
She squeezed out a win over Republican
It's unclear who will challenge Harris in the upcoming election. Joel Fox, a conservative who runs the political website Fox & Hounds, recently bemoaned the lack of Republican opposition.
"One advantage a strong Republican candidate might have in making a run is that Republican donors are looking to support a possible winner in a high-profile office," he wrote on Monday. "But the donors can't give when there is no candidate."
Harris had $3.1 million in the bank for her reelection campaign as of Dec. 31, according to the most recent state report.