He joins an Arsenal side that sit sixth in the Premier League table, five points off the pace in the race for the top four.
The Swans said they had re-signed the 28-year-old for a club record but undisclosed fee on a three-and-a-half year contract.
Aubameyang also signed some balls and Arsenal shirts - although the number was not shown, with the club yet to reveal what the Gabon worldwide will have on his back.
Out of the top eight teams in the Premier League, Arsenal has conceded the most goals with 34.
"After the unpleasant events of the last weeks, we prefer to remember that the story of Pierre-Emerick Aubameyang was a success over more than four years", Dortmund sporting director Michael Zorc said.
Moura, who has made 35 appearances for Brazil, nearly moved to the Premier League in 2012, but PSG beat Manchester United to his signature.
Pierre-Emerick Aubameyang's move to Arsenal was the biggest deal of a frantic deadline day on January 31. Mkhitaryan and Aubameyang linked up to great effect when they played together at Dortmund in the 2015-16 season, scoring 62 goals between them in all competitions. "We wish Pierre-Emerick all the best for his future at Arsenal".
Balanced attack leads Magic to blowout of Lakers
But this may be a two or three step process for them to shed the kind of salary they need to shed while also getting assets. Starting for leading scorer Aaron Gordon (hip), Speights delivered his most productive showing with the Magic .