The Scottish by-elections were triggered when sitting MPs – Flynn and his SNP colleague Stephen Gethins – resigned from the House of Commons after being elected to Holyrood.
Aberdeen is at the heart of the debate around the UK’s energy future, and the UK government has chosen the city as the home of GB Energy – its fledgling publicly-owned energy company.
Lumsden, a former oil and gas worker, said his constituents had sent a message that “the destruction of the oil and gas industry must stop now”.
The North East MSP defeated SNP candidate Richard Thomson, a former MP for Gordon, by a margin of more than 6,000 votes, with the Tories taking almost half of all ballots cast.
Conservative leader Kemi Badenoch has lauded her party’s win in Aberdeen South as a “significant” result, promising that she will “never stop fighting” for its constituents.
She said the result is “particularly significant” due to the support from those who had “never voted Conservative before”.
Badenoch added her party “is working to earn the trust of the country again”, and is “grateful and humbled” that residents of Aberdeen South voted for the Tories.
“Makerfield was about one man’s job. Aberdeen South was about thousands of jobs in oil and gas across our country and the future of an entire city,” she said.