Midfielder Jonathan Pitroipa will join Bundesliga side Hamburg at the end of the season.
The 21-year-old currently plays for German Second Division side SC Freiburg but has agreed a four-year deal which will keep him at Hamburg until 2012.
The Burkina Faso international was available on a free transfer as his current contract expires at the end of the season.
HSV sport director Dietmar Beiersdorfer told the club's official website: "We are delighted to have completed the transfer.
"We have watched Jonathan closely and are convinced that his speed and skill on the ball will help our game."
Pitroipa himself is also delighted at his impending move, saying: "After coming to Europe it was always my goal to play for a big club.
"HSV is a top club with a great environment and a very strong team."