The 19-year-old is regarded as one of the best young defenders in the country, having made his first-team debut for Chelsea against Arsenal in the Premier League earlier this season.
Head coach Graham Potter said, “We are really pleased to have secured the signing of a really exciting young talent in Tariq.
“I am now looking forward to working with Tariq on the training pitch to help him develop further, and I’m sure our supporters are looking forward to seeing him in an Albion shirt.
“With his pace and technical ability, Tariq provides us with another option on the right side of the pitch both at right-back, where we already have good competition, and also further up the pitch.”
Lamptey can play at right-back or on the right-hand side of midfield and technical director Dan Ashworth says the club are pleased to have brought such a highly-regarded player to the club.
He added, “We have been working on securing young, ambitious players with a high level of technical ability and a strong work ethic.
“Tariq has already achieved a lot for a teenager, with both Chelsea and England, and we’re thrilled he feels he can take the next step forward in his career with us.”
Hillingdon-born Tariq joined Chelsea as a seven-year-old and progressed to their under-18s, making his debut at the age of 16.
In 2019 he was part of England’s squad at the Under-19 European Championships and has also played for Chelsea’s under-23s.
He made his senior debut against Arsenal in the Premier League in December, and made two further appearances for Chelsea in the Emirates FA Cup. He’s also appeared three times in the Leasing.com Trophy, scoring twice in the 3-2 defeat at Walsall.