Brown's 60-minute interview has been described as a "curtain raiser" for the new series, which starts in March.
"I have been trying to secure a Life Stories interview with the Prime Minister since the series was first devised, because he is an absolutely perfect subject for the show," said Morgan.
"He's one of the most famous people in the country, yet remains a man of mystery to many. I have known Gordon Brown for over 15 years - he is a man who has enjoyed great triumph, suffered terrible tragedy, and will soon face the biggest challenge of his career."
Previous Life Stories guests have included Sharon Osbourne, Cilla Black, Dannii Minogue, Vinnie Jones and Katie Price.
The Gordon Brown interview will air on Sunday, February 14 at 10.15pm on ITV1