'Black Tuesday's' industrial action affected major cities across France, including Lyon in the south-east.
Hundreds of train drivers walked off the job, leaving one of the city's main train stations, Lyon Perrache, virtually empty for much of the day.
The state railway SCNF lead the demonstration, with union members carrying flags and fire torches.
The unions fear the government's plans to overhaul the indebted SCNF railway would pave the way for its privatisation.
"Privatisation is a choice of government first. Europe allows it but it is a political choice, dogmatic and we are against it. It will not bring anything to the users, the railroaders or the employees," one CGT protester said.
University students joined the demonstration to protest against President Emmanuel Macron's tightening of entrance requirements.
"The baccalaureate is a guarantee of access to higher education and they are destroying all this. The problem is that there is a lack of resources and investment in faculties and places," one student protester said.
The nationwide strikes caused transport chaos.
The unions have warned major disruptions would occur two days in every five for the next three months.