The 24-year-old wing-back completed his transfer from the Allsvenskan club on a four-year deal that includes a club option for a further year, Hull City's official website confirmed.
Financial details of the deal have not been disclosed by either club, though Swedish outlets including Expressen have reported a total package in the region of 49 million kronor once bonuses are included, with around 27 million kronor said to be guaranteed. Sky Sports has separately suggested a fee closer to £3m.
In three and a half years with the Allsvenskan club, Stroud racked up 28 goals and 14 assists from 109 competitive appearances, establishing himself as one of Mjällby's most productive players before his departure this week. He joined Mjällby from IK Oddevold in January 2023, having previously been rated among the standout young talents outside Sweden's top two divisions before his move up the pyramid.
Primarily deployed as a left-back or wing-back, Stroud had also drawn comparisons for his willingness to get forward, a trait reflected in his goal and assist numbers over the past three seasons.
The Sweden international featured in all four of his country's matches at the 2026 World Cup, adding tournament pedigree to a résumé that had also attracted interest from Serie A side Genoa, who were reportedly in contention for his signature before Hull City moved ahead in the race.
Hull City, managed by Sergej Jakirović, have been busy strengthening the squad across several positions this summer as they prepare for life back in the top flight, with Stroud's attacking output from wing-back seen as a key part of that rebuild.
"I am super happy and super excited to get started here. When I first heard of the interest, it was the only thing I wanted to do," Stroud said.
"I spoke with the chairman and I got an even better impression of the club and everything around it.
"I have individual hopes to play at the highest level possible. When an opportunity like this comes, it's not something you take lightly. To do it here in Hull is a very exciting opportunity.
"It was a dream of mine to play in the Premier League. I am super excited to get this opportunity and hopefully create something magical this season."