Despite the Liberal's victory, both the Labour and Conservative candidates claimed victories following an increased share of the vote.
The election wa called following the resignation of Lib Dem Tim Farron.
Michelle McGrath Edwin won with 48 per cent of the vote, closely followed by Matthew Vincent Tomlinson for Labour.
Mrs Edwin said: "I'd like to say a big thank-you to the voters, all of my helpers and especially Mark Alcock, my agent.
"And I'd also like to thank my opponents for a very well-run campaign.
"This is a good result for us. Obviously the people here believe in our work and we will continue to work hard not just here, but throughout South Ribble.
"There were a number of issues which we highlighted here in our campaign. Facilities for young people in the area, to help keep them off street corners, are lacking.
"And we'd like to see an improvement in the transport systems in the area -- the railway station here is a disgrace."
Labour candidate Matthew Tomlinson was upbeat about his defeat. He said: "This has been a good result from my perspective with a swing of about four per cent to us from the Lib Dems.
"We lst be around 1,900 votes at the last county election and by a much smaller margin this time.
"We'll be back in 12 months time!"
Conservative candidate John Otter added: "I'm disappointed with the result but pleased that the Conservative vote is higher than before."
An election was called following the resignation of Tim Farron and the turnout was widely regqard
Michelle McGrath Edwin, Liberal Democrat: 1,721
Matthew Vincent Tomlinson, Labour: 1,198
John William Michael Otter: 627
Turnout: 32 per cent.
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