The 20-year-old winger has joined from PSV Eindhoven for €40m, signing a seven-and-a-half-year contract.
Madueke spent time in the youth sides of Crystal Palace and Tottenham Hotspurs before moving to PSV in 2018.
The Englishman made 77 appearances for PSV, scoring 21 goals.
He joins the likes of David Datro Fofana, Benoit Badiashile, Joao Felix, Andrey Santos and Mykhailo Mudryk in moving to Stamford Bridge this month.
Madueke told the club's official website: "I'm really pleased to sign with one of the best clubs in the world in Chelsea.
"To return to England and play in the Premier League is a dream for me and my family and I can't wait to get started.
"I am excited for what the future holds, the owner's vision for the future and to be at a club like this and winning at the highest level."
Chelsea chairman Todd Boehly and co-controlling owner Behdad Eghbali said: "We're delighted to bring Noni to Chelsea.
"He's an exciting talent who has proven his quality over the past few years with PSV, playing in a strong European league, and we are thrilled he has chosen to join Chelsea for this next stage of his career.
"We are sure he will form an important part of our team."
