Marine pipeline installation tensioner for use on a pipeline installation vessel, the marine pipeline installation tensioner comprising: - at least one lower track unit and at least one upper track unit, each track unit comprising an endless track (11, 12), a chassis (13, 14), bearing means, e.g. support rollers or the like, mounted on said chassis (13, 14) for supporting the endless track, and one or more track motion control members (15, 16) for effecting controlled motion of the endless track (11, 12), - a tensioner frame, comprising: = multiple tensioner frame supports adapted to support the tensioner frame on a support surface of a pipeline installation vessel; = a lower support frame supporting the at least one lower track unit and an upper support frame supporting the at least one upper track unit, which lower and upper support frame (5, 6) support the lower and upper track unit (2, 3) respectively, such that the lower and upper track unit (2, 3) extend parallel to each other and define a central pipeline transport axis between them, = a set of upper support frame actuators provided between the lower support frame and the upper support frame and adapted to move the upper support frame relative to the lower support frame in a direction substantially perpendicular to the central pipeline transport axis; which upper support frame actuators are squeeze actuators, i.e. are adapted to provide a clamping force for clamping a tubular element between the at least one upper track unit and the at least one lower track unit by pulling the upper support frame towards the lower support frame; and = a set of one or more, preferably four or more, lower support frame actuators, wherein each lower support frame actuator is provided between one of the tensioner frame supports and the lower support frame, and wherein the set of one or more lower support frame actuators is adapted to move the lower support frame, and thus the upper support frame, relative to the support surface of a pipeline installation vessel in a direction substantially perpendicular to the central pipeline transport axis. - at least one lower track unit and at least one upper track unit, each track unit comprising an endless track (11, 12), a chassis (13, 14), bearing means, e.g. support rollers or the like, mounted on said chassis (13, 14) for supporting the endless track, and one or more track motion control members (15, 16) for effecting controlled motion of the endless track (11, 12), - a tensioner frame, comprising: = multiple tensioner frame supports adapted to support the tensioner frame on a support surface of a pipeline installation vessel; = a lower support frame supporting the at least one lower track unit and an upper support frame supporting the at least one upper track unit, which lower and upper support frame (5, 6) support the lower and upper track unit (2, 3) respectively, such that the lower and upper track unit (2, 3) extend parallel to each other and define a central pipeline transport axis between them, = a set of upper support frame actuators provided between the lower support frame and the upper support frame and adapted to move the upper support frame relative to the lower support frame in a direction substantially perpendicular to the central pipeline transport axis; which upper support frame actuators are squeeze actuators, i.e. are adapted to provide a clamping force for clamping a tubular element between the at least one upper track unit and the at least one lower track unit by pulling the upper support frame towards the lower support frame; and = a set of one or more, preferably four or more, lower support frame actuators, wherein each lower support frame actuator is provided between one of the tensioner frame supports and the lower support frame, and wherein the set of one or more lower support frame actuators is adapted to move the lower support frame, and thus the upper support frame, relative to the support surface of a pipeline installation vessel in a direction substantially perpendicular to the central pipeline transport axis. = multiple tensioner frame supports adapted to support the tensioner frame on a support surface of a pipeline installation vessel; = a lower support frame supporting the at least one lower track unit and an upper support frame supporting the at least one upper track unit, which lower and upper support frame (5, 6) support the lower and upper track unit (2, 3) respectively, such that the lower and upper track unit (2, 3) extend parallel to each other and define a central pipeline transport axis between them, = a set of upper support frame actuators provided between the lower support frame and the upper support frame and adapted to move the upper support frame relative to the lower support frame in a direction substantially perpendicular to the central pipeline transport axis; which upper support frame actuators are squeeze actuators, i.e. are adapted to provide a clamping force for clamping a tubular element between the at least one upper track unit and the at least one lower track unit by pulling the upper support frame towards the lower support frame; and = a set of one or more, preferably four or more, lower support frame actuators, wherein each lower support frame actuator is provided between one of the tensioner frame supports and the lower support frame, and wherein the set of one or more lower support frame actuators is adapted to move the lower support frame, and thus the upper support frame, relative to the support surface of a pipeline installation vessel in a direction substantially perpendicular to the central pipeline transport axis.