Manchester United have signed full-back Diogo Dalot from Portuguese champions Porto.

Dalot only made his first-team debut in February but the 19-year-old has moved to Manchester on a five-year deal, with an option for a further year, after Premier League runners-up United activated his release clause.

With out-of-favour Italian Matteo Darmian expected to leave Old Trafford and manager Jose Mourinho desperate to provide veteran right-back Antonio Valencia with more competition, United have turned to the Portugal Under-21 international.

"Joining Manchester United is an unbelievable opportunity for me," Dalot said in a statement on United's website.

"I have grown up in Porto's Academy and I am so thankful for everything they have done for me. But the chance of coming to the biggest club in the world is something I just couldn't turn down.

"I'm excited about working with Jose Mourinho and learning everything I can from such a successful coach. I am looking forward to playing alongside the fantastic players in the squad."

Dalot made seven appearances in all competitions in 2017-18 as Porto won the Primeira Liga crown for the first time since 2012-13 and reached the Champions League's last 16.

A Porto youth product, Dalot played in six matches of Sergio Conceicao's triumphant domestic campaign, which ended Benfica's run of four successive league crowns.

Dalot also played at left-back in Porto's goalless draw in the second leg of their Champions League tie with Liverpool, who won 5-0 on aggregate in March.

The news comes a day after United announced they had reached an agreement to sign Brazil international midfielder Fred from Shakhtar Donetsk.