Shane Ferguson will depart Millwall when his contract expires next month.
The winger made 217 appearances for The Lions between 2015-2021, scoring 12 goals.
After loan spells at Birmingham City and Rangers, Ferguson joined The Lions from Newcastle United, initially on loan, in August 2015 and made the move to South London a permanent one in January 2016.
The Northern Ireland international's debut came at Shrewsbury Town on the opening day of the 2015/16 Sky Bet League One campaign, with 'Fergie' going on to net his first two goals for The Lions in a 4-1 success over Colchester United in the November.
Playing 46 times in a mammoth season which saw the club reach the Southern Area Final of the Johnstone's Paint Trophy and the League One Play-Offs, Ferguson was also named in the Green and White Army's squad for EURO 2016, playing in a 1-0 defeat to Poland.
As Millwall and Ferguson lost out to Barnsley in a Wembley Final in 2015/16, in 2016/17 the pair went one better as the left-winger made 52 appearances, scoring four times in a year which saw The Lions beat Bradford City in the Play-Off Final and win promotion to The Championship.
Also included in that memorable season were Emirates FA Cup scalps over AFC Bournemouth, Watford and reigning Premier League champions Leicester City, with Fergie finding the net in a 3-0 win against the former.
Another 28 appearances followed as Neil Harris' side finished eighth in The Championship in 2017/18, before the 2018/19 season saw one of Fergie's finest moments in a Millwall shirt, as he stepped off the bench to score twice in three minutes, turning an Emirates FA Cup tie at home to Hull City on its head, sending the club through to a Fourth Round tie with Everton.
The ever-dependable Ferguson then played 33 times in 2019/20, before signing off with 16 more appearances in 2020/21 - his final one being in a 1-0 victory against Derby County in March.
Everyone at Millwall Football Club would like to thank Shane for his fantastic service to The Lions and wish him the very best for the future.