Millwall have completed the signing of Zak Sturge from Chelsea for an undisclosed fee.

The 21-year-old defender spent the second half of last season on loan at The Den, making five appearances for Alex Neil's side.

Sturge has signed a "long-term" contract at Millwall and becomes the club's third signing of the summer, after goalkeeper Max Crocombe's arrival from Burton Albion and Josh Coburn's club record move from Middlesbrough.

Sturge made his Lions debut in February's 1-0 away win at Derby County and appeared in Millwall's final three matches of the season.

"We're so pleased to bring Zak in on a permanent basis," Millwall's director of football Steve Gallen told the club's website, external.

"He came in on loan in January and whilst we knew how good of a player he was, Joe Bryan was playing exceptionally well and therefore Zak was unable to get many opportunities on the pitch.

"When he did come in, though, he was excellent. Everyone knows Zak now and how he is [as] a player.

"He has a great left foot and loves to get forward, but he is also good in one-v-one situations defensively."

Millwall will begin the new Championship season away at Norwich City on Saturday, 9 August.