The ex-St Benedict's Catholic College pupil has joined the Lions for an undisclosed fee, bringing his lengthy spell in Suffolk to an end.
Millwall director of football Steve Gallen told the club's website: "I'm delighted to bring Elkan to the club.
"He's a player we've been tracking for some time now, and we've followed his development closely - both at Ipswich Town and through his loan spells in the EFL, where he has picked up valuable experience against senior, physical opposition.
We are pleased to announce the signing of defender Elkan Baggott from Ipswich Town!
Welcome to Millwall, Elks 🤝
— Millwall FC (@MillwallFC) July 15, 2026
"He's a good age, has a real appetite to improve and fits the profile we look for defensively.
"Elkan comes in to bolster our defensive options in an area that has been a real strength for us in recent seasons and we're confident he'll add real competition and quality to that group.
"We're pleased he's chosen to join and we're looking forward to seeing him progress here."
Baggott, 23, first joined Ipswich at under-14 level, progressing through the ranks to reach the first team.
What pleased Danny Cowley after Colchester's game at West Ham
He made seven senior appearances for Town, scoring in a Carabao Cup defeat to Fulham in 2023. Baggott also spent time out on loan at King's Lynn (National League), Gillingham (League Two), Cheltenham Town, Bristol Rovers and Blackpool (all League One).
His contract at Portman Road was due to run until the summer of 2028 but he has now left the Suffolk club.
📰 We can confirm that defender Elkan Baggott has joined Millwall on a permanent deal.
Elkan, who came through the Town Academy and went on to make nine senior appearances, departs with the club's best wishes for the future.
— Ipswich Town (@IpswichTown) July 15, 2026
Baggott was born in Bangkok, Thailand, but has 28 senior caps for the Indonesian national team.
The left-footed centre-back became the first Indonesian to play in the English Football League when he made his Ipswich league debut in a game at Rotherham United in April, 2022.
Baggott now joins up with Millwall, who narrowly missed out on automatic promotion to the Premier League last season, finishing just a point behind Ipswich.
'People still talk about it': Gareth Williams on hat-trick that started U's rise
The Lions subsequently went on to lose to Hull City over two legs, in the play-offs.
Baggott has since flown out to Spain to join Millwall’s pre-season training camp ahead of the upcoming Championship campaign, having signed a long-term contract with the London-based club.