Kampl will wear the number 44 shirt, as he did for Bayer 04, and Leipzig will be the second club he plays for owned by Red Bull after a spell with Red Bull Salzburg in Austria.
Leipzig acquire a versatile player in Kampl
Leipzig head coach Ralph Hasenhüttl told dierotenbullen.com that the acquisition of Kampl "will help us enormously" as he "immediately knows what is going on in the pitch" thanks to his brief spell with Hasenhüttl at VfR Aalen in 2012.
Kampl played just three matches for Aalen in the 2.Bundesliga after joining from 3.Liga side VfL Osnabrück for €250,000 but his two goals and three assists drew the attention of Red Bull Salzburg, who paid €3m to lure him to Austria.
The 26-year-old is equally capable as a central midfielder or a winger and undertook a more defensive role at Leverkusen rather than the creative attacking role he excelled in during his two and a half seasons with Salzburg.
Hasenhüttl continued by saying that Kampl "has matured and has developed" since his spell with Aalen and brings Leipzig "all the attributes we need" such as "his speed and his ability on the ball".
Leipzig's sporting director Ralf Rangnick said that he "left [Kampl] only with a heavy heart from Salzburg" after moving to Germany following his time as Salzburg's sporting director, adding that "Leipzig was at this time understandably not an option for Kevin."
Rangnick said that he is a "big fan of his creative way to play football" which "fits perfectly into our game system", adding that his previous spell with Kampl at Salzburg means he knows Leipzig's "game philosophy very well and will need only a little start-up time."
Slovenian international hoping to further his development at Leipzig
The Slovenia midfielder said that "prerequisites for developing as a footballer are simply outstanding" at Leipzig, with the club's "family atmosphere" one of the deciding factors in the move.
He continued by saying that he is "grateful to Leverkusen for the past two years" and is thankful "that the club has enabled me to move to Leipzig", where he hopes to "go to the next step" in his career.
The midfielder initially spent time with Leverkusen's under-19 squad and moved on loan to Greuther Fürth in 2010, before spells at Osnabrück and Aalen followed.
His performances at those two clubs led him to the Austrian Bundesliga with Salzburg where he went on to make 109 appearances, scoring 29 goals and recording 54 assists playing either as a winger or a number 10.
Bundesliga giants Borussia Dortmund came calling in 2015 and Kampl spent seven months with Der BVB before returning to Bayer Leverkusen on a five-year deal, where he would go on to make 73 appearances and was deployed in a defensive role in the centre of midfield.