Simon Roscoe Blevins,Â of Andover Street, in Burngreave, was givenÂ a 16-month prison sentence on Wednesday.
He and fellow campaigners had been found guilty of causing a public nuisance by climbing on top of lorries outside a shale gas drilling site in Lancashire, operated by Cuadrilla.
More than 100 people gathered outside Sheffield Town HallÂ last night to demonstrate their support for the 26-year-old, who is a soil scientist at the University of Sheffield,Â and for the two other campaigners put behind bars.
Those present, including his partner Sarah Jane Palmer, staged a three-minute silence, lit candles and sang songs.
Organiser Jenny Gerrans, of Frack Free South Yorkshire, claimedÂ the sentences may have been intended to send a message that direct action would not be tolerated but they would only serve to strengthen public opposition to fracking.
'This gathering was a necessary, urgent response to a devastating situation. Roscoe's partner, friends and colleagues love him dearly, and we wanted to connect with each other in person, in our city...
'We need to tackle climate change by investing in renewable energy, not fossil fuels. Roscoe and his fellow inmates will be proud of us for continuing to raise awareness while they can't."
Thursday's gathering came two weeks before campaigners are due to descend on Sheffield forÂ the Global Frackdown Carnival at Barker's Pool.
Ms Gerrans added: 'If Roscoe wasn't in prison he would have been inspiring people from the top of the city hall steps, waving banners, and blowing bubbles... We miss him already but his actions will only add fuel to our frack-free fire!'
Mr Blevins is a keen dancer and runner, who completed this year'sÂ Sheffield Half Marathon wearing a hat in the shape of a fracking rig.
Ms Gerrans said he was a '˜strong' and '˜positive' character who would '˜make the most' of his time in prison and would be happy to know his actions had raised awareness of the cause.
Sentencing Mr Blevins and his fellow defendants,Â Judge Robert Latham said that given the disruption they had caused to Cuadrilla and members of the public immediate custody was the only '˜sufficient punishment'.
Cuadrilla's chief executive Francis Egan said following the hearing: 'We have always respected the right to peaceful and lawful protest. However, we will continue to condemn unlawful, irresponsible and reckless behaviour that at best inconveniences and costs law abiding local business and commuters and at worst puts them at risk of harm.'