Hybrid drive system for a motor vehicle, comprising: - an internal combustion engine, which has a first output shaft, - an electric machine, which has a rotor having a rotor shaft as a second output shaft, and - a transmission, which has a four-shaft first planetary gear set, a second planetary gear set, a first shifting element, a second shifting element, a third shifting element and a third output shaft, wherein: ∘ the four-shaft first planetary gear set has a first shaft, a second shaft, a third shaft and a fourth shaft, ∘ the second planetary gear set has a first element, a second element and a third element, ∘ the first shaft, the second shaft, the third shaft and the fourth shaft are rotatable relative to one another and can be connected to one another in a rotationally fixed manner by means of the second shifting element, ∘ the first output shaft is coupled or can be coupled to the first shaft in a rotationally fixed manner, ∘ the rotor shaft is coupled or can be coupled to the second shaft in such a way that torques from the rotor shaft can be introduced into the transmission via the second shaft, and ∘ the third shaft can be connected to the third output shaft in a rotationally fixed manner by means of the first shifting element, wherein the fourth shaft is connected or can be connected to the first element of the second planetary gear set in a rotationally fixed manner, characterized in that the first shaft comprises a first sun gear of the first planetary gear set and the third shaft comprises a second sun gear of the first planetary gear set. - an internal combustion engine, which has a first output shaft, - an electric machine, which has a rotor having a rotor shaft as a second output shaft, and - a transmission, which has a four-shaft first planetary gear set, a second planetary gear set, a first shifting element, a second shifting element, a third shifting element and a third output shaft, wherein: ∘ the four-shaft first planetary gear set has a first shaft, a second shaft, a third shaft and a fourth shaft, ∘ the second planetary gear set has a first element, a second element and a third element, ∘ the first shaft, the second shaft, the third shaft and the fourth shaft are rotatable relative to one another and can be connected to one another in a rotationally fixed manner by means of the second shifting element, ∘ the first output shaft is coupled or can be coupled to the first shaft in a rotationally fixed manner, ∘ the rotor shaft is coupled or can be coupled to the second shaft in such a way that torques from the rotor shaft can be introduced into the transmission via the second shaft, and ∘ the third shaft can be connected to the third output shaft in a rotationally fixed manner by means of the first shifting element, ∘ the four-shaft first planetary gear set has a first shaft, a second shaft, a third shaft and a fourth shaft, ∘ the second planetary gear set has a first element, a second element and a third element, ∘ the first shaft, the second shaft, the third shaft and the fourth shaft are rotatable relative to one another and can be connected to one another in a rotationally fixed manner by means of the second shifting element, ∘ the first output shaft is coupled or can be coupled to the first shaft in a rotationally fixed manner, ∘ the rotor shaft is coupled or can be coupled to the second shaft in such a way that torques from the rotor shaft can be introduced into the transmission via the second shaft, and ∘ the third shaft can be connected to the third output shaft in a rotationally fixed manner by means of the first shifting element, wherein the fourth shaft is connected or can be connected to the first element of the second planetary gear set in a rotationally fixed manner, characterized in that the first shaft comprises a first sun gear of the first planetary gear set and the third shaft comprises a second sun gear of the first planetary gear set.