Chelsea are now in pole position for Aubameyang, after missing out on Romelu Lukaku and failing to sign Alvaro Morata from Real Madrid
The Gabon international finished last season, as the highest goal scorer in Bundesliga, netting 40 goals in total.
The 28-year-old was linked with a move to Paris Saint-Germain and Real Madrid earlier in the summer, but it appears he will be playing his football at Stamford Bridge in the 2017/2018 campaign.
The move is set to spark a striker merry-go-round, as Dortmund have now entered formal talks with Arsenal for France striker, Olivier Giroud.