A pipeline breakaway coupling (10) comprising a pair of shut-off valve housings (12) clamped to each other by means of a detachable collar (14). The shut-off valve housings (12) define a hollow bore (16) along which flowable material may flow and the collar (14) permits the shut-off valve housings (12) to separate from each other on operation of an actuation mechanism (18) operably engaged with the collar (14). A shut-off valve (20) is located within the hollow bore (16) of each shut-off valve housing (12). Each shut-off valve (20) includes a shut-off valve member (22) movable between a valve open position and a valve closed position in which the shut-off valve member (22) shuts off the flow of any flowable material through the hollow bore (16). Each shut-off valve member (22) is biased to move to its valve closed position on separation of the shut-off valve housings (12). The collar (14) includes a pair of collar members (26,28). Each of the collar members (26,28) is pivotably coupled to the other at or towards a first end (26a,28a) so as to allow pivotable movement of the collar members (26,28) relative to each other. The collar members (26,28) are secured to each other at or towards their other, second ends (26b, 28b), so as to clamp the collar members (26,28) about the shut-off valve housings (12), by means of a breakaway coupling mechanism (30). The actuation mechanism (18) includes an actuator (32) and a driving assembly (38) to drive the actuator (32) from an extended position to a retracted position on operation of the actuation mechanism (18). The actuator (32) breaks the breakaway coupling mechanism (30) on driving movement of the actuator (32) into its retracted position.