Bicycle gearshift, comprising: - an actuation linkage configured to deform in order to move a derailleur of the gearshift, the actuation linkage comprising a first body configured to be rotatably connected to a bicycle frame, a second body configured to support the derailleur of the gearshift and a pair of articulation rods that connect the first body and the second body; - a connection member for connecting the actuation linkage to the bicycle frame, wherein the first body is rotatably connected to the connection member at a rotation axis and the connection member is configured to be fixed to the frame; - a locking device acting between said connection member and said first body and selectively actuatable to shift between a first operative configuration in which said first body is free to move about said rotation axis with respect to said connection member and a second operative configuration in which said first body is held in a predetermined angular position with respect to said connection member; and said locking device comprises a single pin slidable along a sliding axis in a through cavity formed on said first body and comprising an actuation end portion to be actuated in order to command the shifting from said first operative configuration to said second operative configuration, and an opposite locking end portion that, when said locking device is in said second operative configuration, is in abutment against said connection member thus preventing a relative rotation between said first body and said connection member, wherein when said locking device is in said second operative configuration said actuation end portion is arranged at one side of said connection member and said locking end portion is arranged at the other side of said connection member; characterized in that when said locking device is in said second operative configuration said locking end portion is in abutment against a lower surface and a rear surface of said connection member; wherein said locking end portion comprises a stem (34c; 134c) that ends with an enlarged head or that comprises a circumferential recess in which an elastic washer is housed, wherein when said locking device is in said second operative configuration the stem (34c; 134c) is in abutment against said lower surface of said connection member and the enlarged head or the elastic washer is in abutment against said rear surface of said connection member; wherein the abutment between the stem (34c; 134c) and the lower surface of the connection member takes place at a shaped housing seat formed in the lower surface of the connection member. - an actuation linkage configured to deform in order to move a derailleur of the gearshift, the actuation linkage comprising a first body configured to be rotatably connected to a bicycle frame, a second body configured to support the derailleur of the gearshift and a pair of articulation rods that connect the first body and the second body; - a connection member for connecting the actuation linkage to the bicycle frame, wherein the first body is rotatably connected to the connection member at a rotation axis and the connection member is configured to be fixed to the frame; - a locking device acting between said connection member and said first body and selectively actuatable to shift between a first operative configuration in which said first body is free to move about said rotation axis with respect to said connection member and a second operative configuration in which said first body is held in a predetermined angular position with respect to said connection member;