Here, we've had a look at five free agents that Millwall can sign this summer......
Olsson has been without a club since leaving Swansea last summer and would be an ideal fit at The Den to compete with Murray Wallace, who is currently the club's only senior recognised left-back.
The former Tottenham midfielder remains a free agent after being released by Swansea in January and with both Ryan Woods and Jayson Molumby returning to their parent clubs at the end of the season, Carroll would be a shrewd addition to the squad.
Rhodes has endured a difficult season at Sheffield Wednesday - netting just three times in the Championship - but having been one of the the deadliest strikers in the Football League over the past decade, he'd be a great addition for any club.
Naughton's deal at the Liberty Stadium is up at the end of the season and with Millwall in desperate need of someone to provide back-up for Mahlon Romeo, the ex-Spurs defender would be a good signing.