Kampl joined Leipzig from Bayer Leverkusen in the summer of 2017 and has made 220 appearances for the club, scoring nine goals.
The 33-year-old's previous deal would have expired in the summer of 2024.
Kampl has won two DFB-Pokals and one German Super Cup during his stay at the Red Bull Arena.
"Kevin Kampl is a key player in our squad. Not only due to his talents as a footballer and his style of play, but also with regard to his role within the team and the entire club. Kevin embodies what it means to be RB Leipzig like no other and fully identifies with the club," said RB Leipzig sporting director Rouven Schröder.
"As a result, it was a logical decision for both parties to seek to extend his contract until 2026, and to continue the work that Kevin has played a key role in over the last six years. We are extremely pleased that Kevko will continue to play for us in the coming years."
The former Slovenia midfielder added: "I'm incredibly happy and proud that we will continue to work together for two additional years.
"What I've been able to experience here since 2017 is unique. I've said it again and again: RB Leipzig is my club, the city feels like home to me and my family and I just love being here.
"We have an exciting team and as one of the more experienced members of the squad, I really enjoy getting to lead the boys and getting to grow together.
