The Blues have paid an initial £53million to land the one-cap Belgian international from Championship side Southampton, with a further £5m agreed in add-ons.
Liverpool saw multiple bids rejected for the 19-year-old earlier in the summer and have now lost out to Chelsea again, having also seen their late approach for Moises Caicedo turned down before their rivals wrapped up a British record deal worth £115m with Brighton earlier this week.
Lavia completed his medical at Chelsea on Thursday and has penned a seven-year contract through 2030 ahead of competing with Caicedo for a spot in Mauricio Pochettino’s expensively-assembled new-look midfield, potentially making a quick debut in Sunday’s London derby away at West Ham in the Premier League. He will wear the no45 shirt in west London, the same number as he had at St Mary’s.
“I’m really happy join Chelsea and be a part of this exciting project. It’s an amazing football club with a great history and I’m really excited to get started,” said former Anderlecht youngster Lavia, who joined Southampton from Manchester City last summer and made 34 appearances across all competitions.
“I can’t wait to meet all my new team-mates and build a chemistry together to achieve great things together.”
This deal has pushed Chelsea’s transfer spending this summer to around £380m, a sum which includes the imminent arrival of teenage Brazilian striker Deivid Washington from Santos. They are nearing the £1billion mark in total in just three transfer windows under the Todd Boehly-Clearlake ownership.
Chelsea’s co-sporting directors Laurence Stewart and Paul Winstanley said: “We are very pleased to welcome Romeo to Chelsea. He demonstrated his quality in the Premier League last season at Southampton, showing maturity despite his young age, and is a player we have monitored for some time.
“We believe he is ready to make an impact at Chelsea throughout the current campaign, and in the coming years.”
Chelsea will not be signing Michael Olise as had been expected. The Blues triggered his £35m release clause earlier this week, only for the France Under-21 winger to then agree a bumper new four-year contract at Crystal Palace on Thursday.
Instead Chelsea have now held talks with Nottingham Forest over £50m-rated forward Brennan Johnson, but face potential competition for the Welsh international from Tottenham and Brentford, with Forest keen on a deal for Trevoh Chalobah.
Chelsea also sounded out Ajax midfielder Mohammed Kudus - now set for West Ham - and Celta Vigo playmaker Gabri Veiga earlier in the summer window.