Match ends, RB Leipzig 2, FC Red Bull Salzburg 3.
Red Bull Salzburg beat RB Leipzig in the sides' first meeting - a thrilling Europa League Group B game.
Both clubs are linked with the drinks company but Uefa ruled they are distinct enough to compete in Europe.
Austrian champions Salzburg led 2-0 through Munas Dabbur and Amadou Haidara goals - both from bad defending.
Konrad Laimer and a Yussuf Poulsen header got Leipzig level, but Fredrik Gulbrandsen ran onto a Hannes Wolf flick-on for a late winner.
German side Leipzig named five former Salzburg players in their starting XI - including Laimer - but made three changes at half-time after a dreadful first-half performance.
They were founded in 2009 with backing from Red Bull and won four promotions in seven seasons, with the company buying Austria Salzburg in 2005 and renaming the club.
After both sides qualified for Europe last season, European football's governing body Uefa conducted a month-long investigation before allowing them to feature.
Each club made serious behind-the-scenes changes - with the company taking a step back at Salzburg, although it still sponsors both clubs.
Salzburg are known as FC Salzburg in European competition because of Uefa regulations, while German rules ban title sponsorship - hence why Leipzig are called RB, which stands for RasenBallsport - a made-up word which translates as Lawn Ball Sports.
The game was played at Leipzig's Red Bull Arena - also the name of Salzburg's home ground.
Celtic beat Rosenborg 1-0 in the group's other game.
Match ends, RB Leipzig 2, FC Red Bull Salzburg 3.
Second Half ends, RB Leipzig 2, FC Red Bull Salzburg 3.
Attempt missed. Stefan Ilsanker (RB Leipzig) header from very close range is just a bit too high. Assisted by Marcel Halstenberg with a cross following a corner.
Corner, RB Leipzig. Conceded by Marin Pongracic.
Marin Pongracic (FC Red Bull Salzburg) is shown the yellow card for a bad foul.
Yussuf Poulsen (RB Leipzig) wins a free kick on the right wing.
Foul by Marin Pongracic (FC Red Bull Salzburg).
Foul by Yussuf Poulsen (RB Leipzig).
Zlatko Junuzovic (FC Red Bull Salzburg) wins a free kick in the defensive half.
Ibrahima Konaté (RB Leipzig) wins a free kick in the defensive half.
Foul by Amadou Haidara (FC Red Bull Salzburg).
Goal! RB Leipzig 2, FC Red Bull Salzburg 3. Fredrik Gulbrandsen (FC Red Bull Salzburg) right footed shot from the centre of the box to the bottom right corner. Assisted by Hannes Wolf following a fast break.
Attempt missed. Fredrik Gulbrandsen (FC Red Bull Salzburg) right footed shot from a difficult angle on the right is close, but misses to the right. Assisted by Takumi Minamino.
Yussuf Poulsen (RB Leipzig) wins a free kick in the defensive half.
Foul by Marin Pongracic (FC Red Bull Salzburg).
Substitution, FC Red Bull Salzburg. Zlatko Junuzovic replaces Xaver Schlager.
Yussuf Poulsen (RB Leipzig) is shown the yellow card for a bad foul.
Foul by Yussuf Poulsen (RB Leipzig).
Takumi Minamino (FC Red Bull Salzburg) wins a free kick in the defensive half.
Ibrahima Konaté (RB Leipzig) wins a free kick in the defensive half.
Foul by Amadou Haidara (FC Red Bull Salzburg).
Substitution, FC Red Bull Salzburg. Fredrik Gulbrandsen replaces Munas Dabbur.
Goal! RB Leipzig 2, FC Red Bull Salzburg 2. Yussuf Poulsen (RB Leipzig) header from the centre of the box to the centre of the goal. Assisted by Kevin Kampl with a cross.
Attempt missed. Yussuf Poulsen (RB Leipzig) header from the right side of the box misses to the right. Assisted by Diego Demme.
Attempt saved. Matheus Cunha (RB Leipzig) right footed shot from outside the box is saved in the bottom right corner.
Attempt blocked. Kevin Kampl (RB Leipzig) right footed shot from outside the box is blocked. Assisted by Marcel Halstenberg with a headed pass.
Amadou Haidara (FC Red Bull Salzburg) is shown the yellow card.
Diego Demme (RB Leipzig) wins a free kick in the attacking half.
Foul by Amadou Haidara (FC Red Bull Salzburg).
Marcel Sabitzer (RB Leipzig) wins a free kick in the attacking half.
Foul by Munas Dabbur (FC Red Bull Salzburg).
Attempt blocked. Yussuf Poulsen (RB Leipzig) header from the centre of the box is blocked. Assisted by Diego Demme.
Ibrahima Konaté (RB Leipzig) wins a free kick in the defensive half.
Foul by Takumi Minamino (FC Red Bull Salzburg).
Matheus Cunha (RB Leipzig) wins a free kick in the defensive half.
Foul by Diadie Samassekou (FC Red Bull Salzburg).
Foul by Kevin Kampl (RB Leipzig).
Takumi Minamino (FC Red Bull Salzburg) wins a free kick on the right wing.
Foul by Ibrahima Konaté (RB Leipzig).
Xaver Schlager (FC Red Bull Salzburg) wins a free kick on the right wing.