Asher-Smith, 22, added to the 100m crown she won on Tuesday with an imperious performance to decimate the field with a world-leading time of 21.89.
Dutch world champion Dafne Schippers ran a season's best 22.14 but was a distant second to Asher-Smith, who can complete the treble in the 4x100 relay on Sunday.
Jamile Samuel completed the podium after she ran a personal best of 22.37.
“Honestly, I am so stunned,” Asher-Smith told Eurosport.
Normally I am not lost for words but I am just so unbelievably happy.
“I have wanted to get under 22 seconds for a while now so to have done that and win the European champs means so much.”
Dina Asher-Smith of Great Britain celebrates winning gold in the Women's 200 metres final during day five of the 24th European Athletics Championships at Olympiastadion on August 11, 2018 in Berlin, Germany.
Image credit: Getty Images
Asher-Smith, who claimed bronze in the 200m at the Commonwealth Games earlier this year, broke her own British record of 22.07, which has stood since 2015, and has now run world-leading times in both the 100m and 200m events at these championships in Berlin.