The 20-year-old forward has penned a three-year contract at Brisbane Road, with the option of a fourth year.
Ballard, a product of Southampton’s academy, made four senior appearances for the Saints, scoring once. He gained further experience out on loan last season, spending the first half of the campaign at Blackpool, where he netted once in 22 games, before moving to Cambridge United, scoring twice in 17 appearances.
Orient boss Richie Wellens expressed his delight at securing the deal, revealing Ballard was a target for a number of clubs.
“We’ve had eyes on him for a couple of seasons now, and there were a lot of clubs who wanted him, so we’re over the moon that he’s chosen Leyton Orient as his next home,” Wellens told the club’s official website.
The move marks Ballard’s first permanent step away from Southampton as he looks to establish himself in senior football.
