Abstract: A pipeline breakaway coupling (10) comprising a pair of valve housing members (12,14) fixedly attached to each other by means of one or more breakaway coupling members (16). The valve housing members (12,14) define a hollow bore (18) along which flowable material may flow and the breakaway coupling members (16) permit the valve housing members (12,14) to separate from each other when exposed to a tensile load exceeding a predetermined limit. An end cap (26) releasably connected to each valve housing member (12,14) to allow connection of the valve housing members (12,14) to respective inlet and outlet pipelines. A valve cassette (20) is releasably retained between each valve housing member (12,14) and the respective end cap (26). Each valve cassette (20) includes a valve member (22) movable between a valve open position and a valve closed position.