LGV Sud-Est opened in 1981 as the first French high-speed line built for TGV service.
The line connects the Paris and Lyon regions and was France's first dedicated high-speed railway. Its first section was inaugurated on 22 September 1981 by President François Mitterrand, while commercial TGV service began on 27 September. The remaining northern section opened in 1983.
Construction began in 1976 after SNCF research into high-speed rail. The 1973 oil crisis helped push planners toward electric traction and overhead electrification rather than the gas-turbine propulsion considered during earlier TGV studies. The route was designed for 300 km/h operation and used a direct alignment that avoided many urban areas.
LGV means Ligne à Grande Vitesse, or “high-speed line.” LGV Est, LGV Nord, and LGV Atlantique are later routes, so they cannot be the answer to a question about the first TGV high-speed line. LGV Sud-Est helped establish the TGV as a major alternative to domestic air travel between Paris and Lyon.