The 29-year-old joins as a free agent after his contract at Fulham expired on 30 June, following a stellar campaign in west London.
Wilson finished the season with 10 goals and seven assists in the Premier League, the best return by a Fulham player in a single top-flight campaign since Dimitar Berbatov in 2012-13. He was named Fulham's Player of the Year and picked up the BBC's Goal of the Season award for a stunning strike against Crystal Palace.
Leeds United tried to sign the versatile forward last summer, only for Fulham to pull out in the final 24 hours of the window. Boss Daniel Farke has finally got his man, with Wilson turning down interest from elsewhere - reportedly including Aston Villa and Everton - to join a host of familiar faces from the Wales squad.
Speaking to LUTV, Wilson explained what swayed his decision.
"This summer was different. When the season finished and I became a free transfer, I felt Leeds were the team that really showed the interest in me. And as a player, you want to play for a team which you feel like they want you and you feel like they are doing everything to get you. Speaking with the Welsh boys, I think it was pretty clear that this was the place that I wanted to come."
Wilson, capable of playing off the flank or through the middle, has made more than 150 Premier League appearances and won 69 caps for Wales, scoring 17 international goals.
He faced Leeds twice last season and came away impressed by what he saw.
"I think in both of those games I realised what a difficult team they were," he said. "I am just excited to come in, join the group and build on what the team put in place last year."
Wilson also pointed to Leeds' home support as a factor, having experienced the atmosphere at Elland Road first while on loan at Derby County.
"To this day, that is the best atmosphere I have ever played in," he said of that visit. "I remember walking out that night and seeing all the scarves getting waved and you couldn't hear yourself think."
With pre-season under way at Thorp Arch, Wilson says he has used the break to make sure he hits the ground running for Farke's first full season back in the top flight.