Grenoble's relegation to Ligue 2 was confirmed this evening by their thumping defeat at Toulouse and St Etienne's victory at Sochaux.
Paulo Machado opened the scoring for TFC after nine minutes and a second-half brace by substitute Franck Tabanou sealed Grenoble's fate before Andre-Pierre Gignac dealt a further blow five minutes from time.
St Etienne's 2-0 win at Sochaux left Mecha Bazdarevic's bottom-placed side 20 points adrift of safety with six games remaining of the Ligue 1 campaign.
The writing was on the wall from the early stages for the visitors as Gignac seized possession and lashed in a shot from a tight angle. Jody Viviani pushed the ball away but only to Machado, who had the simple job of tapping home.
Moussa Sissoko almost made it 2-0 after 22 minutes when he latched onto Gignac's pass on a counter-attack and fired in a fierce shot which crashed against the bar.
Laurent Batlles tried his luck for Grenoble two minutes later but Mathieu Berson was in the way and deflected his effort away to safety with his knee.
Toulouse goalkeeper Yohann Pele was called into action for the first time just after the half-hour, punching away Nassim Akrour's header from Batlles' corner as Grenoble looked to get back on level terms.
The hosts started the second half as they had done the first - on the front foot - and should have doubled their lead six minutes in when Sissoko found himself clean through on Viviani thanks to Gignac's fine through-ball, but he contrived to miss the target.
The second goal was not far off, however. Machado back-heeled to Tabanou, whose brilliant left-footed shot flew into the top corner after 64 minutes.
Nine minutes later, Tabanou bagged his second of the night by capitalising on a poor clearance and bearing down on Viviani before slotting another fine left-footed shot home.
Grenoble knew their destiny was sealed with Les Verts also winning at Sochaux, but Gignac rubbed further salt in their wounds with a late fourth, controlling the ball well and slotting a low drive past a helpless Viviani.