John Stevens is currently the deputy political editor at the Daily Mail and will join the Mirror's political team in the Autumn.
Mirror editor-in-chief Alison Phillips said: "John is a proven story getter who has broken exclusive after exclusive, including the revelations about Dominic Raab's holiday at the height of the Afghan withdrawal crisis, and we are delighted to welcome him to the Mirror.
"In the last few years the Mirror's political coverage has set the pace in Westminster. We have an outstanding team focussed on breaking stories and holding power to account. Under John's leadership I am confident the team will reach new heights."
John Stevens added: "I am absolutely thrilled to be joining the Mirror in my dream job as political editor at this incredible moment in British political history.
"The Mirror's brilliant political team has led the pack at Westminster in the past year. I cannot wait to get started."
At the Mirror, John joins a political team that includes Kevin Maguire, Ben Glaze, Dan Bloom, Lizzy Buchan, Mikey Smith and Aletha Adu.