The Hungary international has extended his stay at Anfield before the start of what will be his fourth campaign with the club and his first under new head coach Andoni Iraola.
Speaking after signing the deal, Szoboszlai described the moment as one of the biggest of his career.
"It's maybe my biggest day," he told Liverpool's official website.
"There are a couple in front of it â- probably when I signed for Liverpool the first one and when I got my baby, of course. But in my football career, I can say this is in the top three.
"Very happy. I can't wait to go again and again and again. I'm just happy to be here, as I said many times."
Since joining Liverpool from RB Leipzig in the summer of 2023, the 25-year-old has established himself as one of the club's key midfielders. He has made 147 appearances in all competitions, scoring 28 goals while playing an important role in the club's recent success.
Szoboszlai helped Liverpool lift the Carabao Cup in his debut season before becoming a key figure in their Premier League title-winning campaign in 2024-25.
Last season was his most productive yet in a Liverpool shirt. He scored 13 goals and provided 12 assists in 53 appearances, performances that earned him the club's Standard Chartered Player of the Season award, voted for by supporters.
Despite those achievements, Szoboszlai insisted he is still aiming to improve.
"There's always more to come. I'm never happy," he said.
"No, I'm happy with myself but I think I can do even better. I think that's why I'm sitting here, because that pushed me since I was a kid: that it was never enough. And I'm thinking the same now."
The midfielder also made it clear that his ambitions remain unchanged as Liverpool prepare for another campaign.
"I want to set the example. I want to be an example also for everyone, as much as I can.
"When I signed, I said I want to win everything. That didn't change for a little moment either. It stayed the same: I want to win everything that is possible in this country, also let's say the Champions League.
"I'm ready to go for it."