Lallana departed Anfield following a six-year stint at the club, during which he made 178 appearances in all competitions; scoring 22 goals and assisting 21.
The 32-year-old was an influential figure in the dressing room; despite injuries, competition for places and age curtailing his time on the pitch.
Upon signing a three-year deal with the Premier League side, Lallana revealed Brighton's ambition, plus the way they "reached out" to him, was the selling point for him.
"I can't wait to get started. It's a breath of fresh air coming here – having my medical; everything is new. It's a challenge I am looking forward to," he said.
"The whole infrastructure and ambition around the club excites me. There is so much young talent and so much ability.
"The manager is highly-regarded, and it was a pretty easy choice for me in the end, especially knowing how much Brighton have reached out. It's nice to know that you're wanted – I think it's a perfect match."
😁 The first interview with the new man!
Lallana reiterated the feeling of a "perfect match" as he highlighted the vast experience he has of playing top-flight football, which the Seagulls are yet to procure.
"I look how ambitious the chairman is to start with and how highly the manager is regarded since he has come into the club," Lallana added.
"He has changed the dynamics and the staff and to do that while keeping the team in the division shows he has done a fantastic job.
"I looked at all those aspects, the squad, the training ground facilities, the stadium - and it was a perfect fit really. I am really excited to get stuck into the challenge and hopefully we can push on again next season.
"Brighton are on an upward curve. I have played against them a lot, and remember seven or eight years ago when Southampton and Brighton were both in League One, so they have been progressing for years now.
"I think we're at the stage here where we can really push on in the Premier League. I have got a lot of experience playing in the Premier League and at a high level.
"I know what's required and how we can improve. If I can help just a little bit in that journey to improve Brighton as a whole, and as a squad, then I will be very happy."
Lallana will undoubtedly be a welcome visitor back to Anfield next year, with the midfielder hugely popular in the squad, especially with Reds skipper Jordan Henderson.
"Whatever team gets him is [in for] a big treat, because he is a massive player," Henderson said of his now-former teammate. "He is a great lad and a great leader in the group and the dressing room.
"And even if you haven't seen him much on the pitch, he still has a massive influence in the dressing room, so we will definitely miss him."
All the best, Adam!