The newly-promoted Swans have reached an agreement to borrow the services of the Tottenham Hotspur defender for a season, subject to review by both teams in January.
"We are delighted to have agreed terms with Tottenham regarding a deal for Steven,” Swansea chairman Huw Jenkins told his club’s official website. "The deal has been very close for the last couple of weeks. I met [Tottenham chairman] Daniel Levy at a Premier League meeting in Darlington and spoke at length about Steven.”
"Steven is a young, upcoming player that is a big talent, and he is looking forward to being part of our squad in the Premier League.
"It is an exciting signing for us. There was other interest in him prior to this deal being agreed, but Tottenham felt it was perfect for Steven to continue his deal here."
The 19-year-old has previously undertaken loan periods at Yeovil and Bristol City since joining Spurs in 2009.