The club confirmed the deal on Monday via a release.
The 23-year-old moved to Portugal from Olympique Marseille during the summer and arrived at Porto with extraordinary expectations. He failed to make the transition to the Dragons' philosophy, and he was considered something of a transfer flop.
Imbula flashed an enormous amount of quality with Marseille, however, and he showed glimpses of what he could do with Porto, as you can see in the video below:
The Frenchman, who was born in Belgium and has confirmed that he wants to play for the Red Devils, per L'Equipe (h/t Bleacher Report UK's Andrew Gibney), has been linked with a move to the Premier League throughout the January window, according to the French newspaper (via talkSPORT).
He finally "cracked" late in January, taking to social media to express his desire to leave in a not-so-subtle way. As reported by Sport Witness, he shared an article saying Stoke had made an offer for his services on his verified Facebook page, angering Porto fans in the process.
His time at the club was destined to end from that point onward, and the Potters pounced. The London Evening Standard's Joe Krishnan couldn't believe it when he first found out Stoke were planning a move:
Joe Krishnan @joekrishnan
Imbula to Stoke arguably one of the signings of the window if it goes through. Mark Hughes recruiting brilliantly.2/1/2016, 11:49:35 AM
While he may have been a bust with Porto, it's worth remembering Imbula was regarded as a major midfield prospect just months ago. He's hugely talented, and his playing style, built around raw physical strength, makes him a fantastic fit for the Premier League.
He made a strong impression in the UEFA Champions League against Chelsea and has the potential to play regularly on the biggest stage of European football. Similar to the deal for Xherdan Shaqiri, Stoke are landing a player who likely could have held his own at a bigger club.
Manager Mark Hughes is assembling an impressive squad at the Britannia Stadium, and the on-pitch results have reflected the club's ambitions of late. The deal for Imbula is yet another step in the right direction, and while the midfielder carries some risks, this transfer could easily be the steal of the winter window.