The 24-year-old joins the club for an undisclosed fee, signing a four-year deal at Craven Cottage.
Mawson was born just 15 miles from Fulham's ground in Hillingdon and came through the ranks at Brentford.
A host of loan spells followed, before Mawson was snapped up by Barnsley in 2015.
The England U21 international was with the 'Tykes' for just a season before being lured to the Premier League by Swansea and he hasn't looked back during his two seasons in the English top flight, establishing himself as a competent and reliable defender and earning his first full England call-up back in March.
However, Swansea's relegation last season always meant that he was likely to leave, with Fulham's closeness to his home proving the key factor as they saw off rival interest from Burnley to secure his signature.
Speaking to Fulham's official website, Mawson said he was delighted to have signed on the dotted line. “I’m really happy to get this over the line and join Fulham," he enthused. "I’m excited by the project going on here and the football being played last season was lovely on the eye but also effective and I can’t wait to be a part of it and get going.
“I’m excited to be a part of this great Club moving forward and to help achieve success in the Premier League."
August 2, 2018