An artificial heart valve comprises a support structure defining an aperture for blood flow and a flexible leaflet connected to the support structure along first and second at least partially straight lines of attachment, wherein the leaflet is movable relative to the support structure between an open configuration in which the leaflet permits blood flow through the aperture and a closed configuration in which the leaflet restricts blood flow through the aperture. A lateral cross-section taken through the leaflet defines an outwardly convex portion, an outwardly concave portion and a junction between the convex and concave portions. The heart valve may be configured for implantation in a human or animal subject. A method of manufacturing a heart valve and a former for use in such a method are also disclosed.