The England midfielder has made nearly 500 appearances for the club.
Liverpool signed Jordan Henderson from Sunderland on this day in 2011.
The deal for the 20-year-old England midfielder was reported to be worth £16million.
“Obviously it’s hard to leave your local club. I’m a Sunderland lad, I’ve supported them all my life,” Henderson told the Liverpool website.
“But this is a massive opportunity for me. I’m really excited by it.
“Coming to a massive club like Liverpool, there is always going to be competition.
“Hopefully I can keep working hard, keep improving, and get my chance on the pitch.”
Henderson picked up a winners’ medal in his first season at Anfield as Liverpool beat Cardiff in a Wembley penalty shoot-out to win the 2012 League Cup.
He became Liverpool’s vice-captain in September 2014 and was appointed skipper the following July after Steven Gerrard’s departure.
Henderson has gone on to lift seven trophies as Liverpool captain under Jurgen Klopp – the Premier League, Champions League, FA Cup, Carabao Cup, FIFA Club World Cup, UEFA Super Cup and Community Shield.
He was named the 2019-20 Football Writers’ Association’s Footballer of the Year as Liverpool ended a 30-year wait to become champions of England.
The 75-times capped Henderson has played 492 games for Liverpool, with only Jamie Carragher and Gerrard making more Premier League appearances for the club.