Gulacsi joined Leipzig from Austrian side RB Salzburg in the summer of 2015 and has made 222 appearances in all competitions in his time at the club.
The 31-year-old Hungarian shot stopper has been instrumental in RB Leipzig’s rise to the upper echelons of Germany and European football, having joined the club when they were in the second division.
Last season, Gulacsi helped Julian Nagelsmann’s men reach the UEFA Champions League semi-finals and having pushed Bayern Munich all the way in the Bundesliga this term, second-placed Leipzig will get the chance to win a major silverware for the first time in their history when they play Borussia Dortmund in the DFB-Pokal final next week.
"The club and I have been on a special journey together since 2015, from the second division to the Champions League semi-finals and next week to the final of the DFB-Pokal once again," Gulacsi told RB Leipzig's website.
"It has been and still is an incredible and very successful time and we want to continue it together. My family and I feel incredibly at home here - at the club, the city and the region. Leipzig has become a second home for us and the atmosphere of feeling good is exactly what is important for me to bring my best-possible performances.
"My wife and I always get goosebumps looking back to the cup match against FC Bayern in 2017, when there were Gulacsi chants for the first time. That was a very special moment that showed me how much our fans are behind me. I'm proud to have earned this support and I'm looking forward even more to games that can take place with fans in the stadium again."