Fiorina, who would face Assemblyman Chuck DeVore of Irvine in the Republican primary in June, announced that she had filed papers with the Internal Revenue Service to start exploring a candidacy.
"The people of California have serious concerns about job creation, economic growth and the role of government in solving problems that touch each of our lives," Fiorina said in a written statement.
Her personal wealth would make Fiorina a heavy favorite for the Republican nomination. But she would have a tough fight to unseat Boxer, a Democrat seeking a fourth term. And Fiorina is opposed to abortion, which puts her at odds with most California voters.
Fiorina was fired from Hewlett-Packard after a rocky tenure.