Tim Cahill has rejoined Millwall 13 years after leaving the club.
The 38-year-old has signed a deal for the Championship club until the end of the season.
Cahill completed a medical at on Monday before signing his contract alongside manager Neil Harris and Millwall’s chief executive Steve Kavanagh.
Manager Neil Harris told the club’s website: “He is a different player to what he was years ago – he plays a little higher up the park now.
“At 38, he is in terrific shape. To start with, we are thinking about impact – someone to come off of the bench and give us that little lift, someone to lift the crowd and someone to pass on that knowledge when in front or behind.”
Cahill scored 57 goals in 251 appearances for Millwall between 1998 and 2004 before his form earned him a move to Everton where he scored 56 goals in the Premier League.
More recently he has been playing in his homeland for Melbourne City after spells in the United States and China.
Cahill will wear the No 7 shirt although he is not available for selection for Millwall yet.