According to ESPN's Stephan Uersfeld, the 16-year-old has long been a source of interest for the Bundesliga outfit, whose training facilities he recently made a visit to, and he has also been linked with the likes of United and Bayern Munich.
Sport Bild (h/t Bundesliga writer Manuel Veth) reported details of his proposed move to BVB:
Dortmund's current record signing is Mats Hummels, whom they re-signed from Bayern last summer for a reported €30.5 million (£26.7 million).
According to Uersfeld, Dortmund are likely to sign him in a similar manner to the way they landed Jadon Sancho from Manchester City in 2018, when they are believed to have paid a training compensation fee of €7 million (£6.1 million).
Uersfeld added that while compensation for Bellingham is likely to exceed the payment for Sancho, it won't be as high as €35 million (£30.6 million).
Constantin Eckner of football analytics company Spielverlagerung believes he'd still be worth it if it was:
Wednesday's FA Cup clash with Leicester City would have provided a good opportunity to see how he fared against Premier League opposition, but manager Pep Clotet is set to rest him, per TalkSport's Tom Ross:
Clotet is a huge admirer of his young charge, though. Clotet said in October: "He can go forward as well, he can defend, he is very complete and despite being only 16 he handles the physicality of the midfield very well."
The teenager has split his time this season between both flanks and central midfield, scoring four goals and assisting three in 34 games in all competitions.
He's made 31 of those appearances in the Championship, starting 24 of them.
Per WhoScored.com, he has won 72 of the 100 tackles he's attempted and made 31 blocks and 21 interceptions. He has also created 20 chances and completed 32 successful dribbles.