A large, club-shaped secretory organelle that forms part of the apical complex of an apicomplexan parasite, and consists of a bulbous body and a narrow electron-dense neck that extends through the conoid at the apical tip of the parasite. The rhoptry necks serve as ducts through which the contents of the rhoptries are secreted after attachment to the host has been completed and at the commencement of invasion. Rhoptry proteins function in the biogenesis and host organellar association of the parasitophorous vacuole.