A hybrid vehicle power train comprising: - three drive sources (MT, ME1, ME2) including a first electric machine, a second electric machine and a heat engine having parallel shafts; - and a gearbox having four parallel shafts and having gears, comprising: - a common output shaft to the wheels of the vehicle; - and three parallel and laterally offset input shafts (11, 5, 6) including: -- a first input shaft which is connected to the first electric machine and supports a first coupling; -- a second input shaft which is connected to the second electric machine and supports a second coupling; -- an input shaft which is connected to the heat engine and supports a coupling, referred to as the heat coupling, and a group of three rotationally coupled idler gears (28, 27, 26), including a first gear which permanently meshes with a first idler gear supported by the second input shaft of the second electric machine, a gear which permanently meshes with a fixed secondary line gear supported by the common output shaft, and a second gear which permanently meshes with a second idler gear supported by the second input shaft of the second electric machine; wherein each of the couplings (CT, CE1, CE2) enables the transfer of the torque provided by the input shaft (11, 5, 6) which supports it to the common output shaft to the wheels of the vehicle to be selectively established. - three drive sources (MT, ME1, ME2) including a first electric machine, a second electric machine and a heat engine having parallel shafts; - and a gearbox having four parallel shafts and having gears, comprising: - a common output shaft to the wheels of the vehicle; - and three parallel and laterally offset input shafts (11, 5, 6) including: -- a first input shaft which is connected to the first electric machine and supports a first coupling; -- a second input shaft which is connected to the second electric machine and supports a second coupling; -- an input shaft which is connected to the heat engine and supports a coupling, referred to as the heat coupling, and a group of three rotationally coupled idler gears (28, 27, 26), including a first gear which permanently meshes with a first idler gear supported by the second input shaft of the second electric machine, a gear which permanently meshes with a fixed secondary line gear supported by the common output shaft, and a second gear which permanently meshes with a second idler gear supported by the second input shaft of the second electric machine; - a common output shaft to the wheels of the vehicle; - and three parallel and laterally offset input shafts (11, 5, 6) including: -- a first input shaft which is connected to the first electric machine and supports a first coupling; -- a second input shaft which is connected to the second electric machine and supports a second coupling; -- an input shaft which is connected to the heat engine and supports a coupling, referred to as the heat coupling, and a group of three rotationally coupled idler gears (28, 27, 26), including a first gear which permanently meshes with a first idler gear supported by the second input shaft of the second electric machine, a gear which permanently meshes with a fixed secondary line gear supported by the common output shaft, and a second gear which permanently meshes with a second idler gear supported by the second input shaft of the second electric machine; -- a first input shaft which is connected to the first electric machine and supports a first coupling; -- a second input shaft which is connected to the second electric machine and supports a second coupling; -- an input shaft which is connected to the heat engine and supports a coupling, referred to as the heat coupling, and a group of three rotationally coupled idler gears (28, 27, 26), including a first gear which permanently meshes with a first idler gear supported by the second input shaft of the second electric machine, a gear which permanently meshes with a fixed secondary line gear supported by the common output shaft, and a second gear which permanently meshes with a second idler gear supported by the second input shaft of the second electric machine;