An internal combustion engine, comprising: - a variable compression ratio mechanism arranged to vary an engine compression ratio in accordance with a rotation position of a control shaft; - an actuator arranged to vary the rotation positon of the control shaft; - an arm portion extending from the control shaft in a radially outward direction; - a lever arranged to link the actuator and the arm portion; - a link pin which penetrates the lever and the arm portion, and which rotatably links the lever and the arm portion; and - a wall portion which confronts an end surface of the link pin irrespective of the rotation position of the control shaft, and which retains the link pin to the lever or the arm portion, wherein: - mounting positions of a stopper including the wall portion to an internal combustion engine main body are set on both sides of the link pin in an axial direction of the link pin, - the stopper includes: - said wall portion as one end-side side wall which is a wall portion confronting one end surface of the link pin as a control shaft side link pin; - another end-side side wall which is a wall portion that is parallel to the one end-side side wall and that confronts the other end surface of the control shaft side pin; - a bottom wall connecting the one end-side side wall and the other end-side side wall; - one end-side flange which has a plate shape, which protrudes from the one end-side side wall, and which is fixed to a portion of an upper oil pan that has a relatively high rigidity; and - another end-side flange which has a plate shape, which protrudes from the other end-side side wall, and which is fixed to a portion of the upper oil pan that has a relatively high rigidity, and - the one end-side flange and the other end-side flange are set on the both sides of the control shaft side link pin in the axial direction of the control shaft side link pin. - a variable compression ratio mechanism arranged to vary an engine compression ratio in accordance with a rotation position of a control shaft; - an actuator arranged to vary the rotation positon of the control shaft; - an arm portion extending from the control shaft in a radially outward direction; - a lever arranged to link the actuator and the arm portion; - a link pin which penetrates the lever and the arm portion, and which rotatably links the lever and the arm portion; and - a wall portion which confronts an end surface of the link pin irrespective of the rotation position of the control shaft, and which retains the link pin to the lever or the arm portion, - mounting positions of a stopper including the wall portion to an internal combustion engine main body are set on both sides of the link pin in an axial direction of the link pin, - the stopper includes: - said wall portion as one end-side side wall which is a wall portion confronting one end surface of the link pin as a control shaft side link pin; - another end-side side wall which is a wall portion that is parallel to the one end-side side wall and that confronts the other end surface of the control shaft side pin; - a bottom wall connecting the one end-side side wall and the other end-side side wall; - one end-side flange which has a plate shape, which protrudes from the one end-side side wall, and which is fixed to a portion of an upper oil pan that has a relatively high rigidity; and - another end-side flange which has a plate shape, which protrudes from the other end-side side wall, and which is fixed to a portion of the upper oil pan that has a relatively high rigidity, and - the one end-side flange and the other end-side flange are set on the both sides of the control shaft side link pin in the axial direction of the control shaft side link pin. - said wall portion as one end-side side wall which is a wall portion confronting one end surface of the link pin as a control shaft side link pin; - another end-side side wall which is a wall portion that is parallel to the one end-side side wall and that confronts the other end surface of the control shaft side pin; - a bottom wall connecting the one end-side side wall and the other end-side side wall; - one end-side flange which has a plate shape, which protrudes from the one end-side side wall, and which is fixed to a portion of an upper oil pan that has a relatively high rigidity; and - another end-side flange which has a plate shape, which protrudes from the other end-side side wall, and which is fixed to a portion of the upper oil pan that has a relatively high rigidity, and - the one end-side flange and the other end-side flange are set on the both sides of the control shaft side link pin in the axial direction of the control shaft side link pin.