The prolific songwriter and producer, who has worked with the likes of Beyonce, Adele, Madonna and Jennifer Lopez, confirmed to British newspaper The Sun that he will feature on Harry's debut solo album.
Talk of Harry's album is gathering pace as he is at the centre of a record label bidding war, officially registered four new solo songs, titled Already Home, Coco, Endlessly, and 5378 Miles and signed with new management last year (15) ahead of the launch of his solo career during One Direction's hiatus.
"We’re going to be writing something for his solo album," Ryan told The Sun. "We did work together in London a while ago but we definitely will again."
Ryan also gave an insight into Harry's drive as an artist: "He’s always writing songs. He’s a brilliant writer."
The 36-year-old Oklahoma native was an integral part of Adele’s songwriting team for 21 and helped write songs Rumour Has It and Turning Tables. He also contributed to track Remedy for smash album 25.
Ryan was in London to promote the release of OneRepublic’s fourth studio album, which he promised will be out before autumn (16).
The group have worked with a variety of music pals including veteran rocker Peter Gabriel.
"I just recorded Peter Gabriel. One of the first songs I did for it was with Romy from The xx and I’m hoping Pharrell will be on board," he added.