It delivered 27 bikes each to Brighton Bike Hub, based just off Lewes Road, and Cranks, in Kemptown – both not-for-profit workshops who aim to promote and provide affordable cycling.
They refurbish and recycle bikes and parts for sale at low prices, and offer space and advice for DIY repairs and maintenance.
The rail company picked out the machines in best condition from all those abandoned on the West Coastway route between Portsmouth and Brighton over the past few months.
Charities in Chichester and Newhaven have also received sizeable donations.
The railway company collects a steady stream of bikes abandoned at stations – many in surprisingly good condition.
The bikes are held for at least two months for the owners to retrieve them.
Duncan Blinkhorn of Brighton Bike Hub said: “It’s great to receive these bikes at a time when so many people are wanting to cycle.
“Our volunteer team have immediately set about fixing the bikes up to get them back on the road and into the hands of people who will really appreciate them.”
Al Bailey of Cranks said: “Thank you so much from all of us here for the kind donation of over two dozen bikes.
“The donations really help keep organisations like us running and enable us to help as many people from different walks of life as possible We have already been busy repairing and stripping them for all the useful parts and they have gotten plenty of cyclists back on the road.
“Two bikes have already been sold and the money has gone back into the project.
“Another was given to an NHS organisation helping people to move forward in healthy pathways and the rest are definitely destined for good things.”
Southern has now established several partnerships with NHS trusts, councils, charities and community bike recycling schemes to find new owners for the abandoned machines.
Chris Fowler, Customer Services Director for Southern, said: “It’s fantastic to be working with all our partners to promote healthy, green transport by extending the life of previously unwanted bikes.
“Brighton’s community workshops can ensure these bikes are made roadworthy and find deserving new owners.
“And by encouraging young people to cycle and look after their bikes we’re creating lasting benefits for their future.
“At this challenging time, we’re proud to help keep Britain moving safely and sustainably.
“We’re building strong local partnerships right across our network to help communities recover and prosper.”