Abstract: The invention provides a marine drive unit (1), such as an outboard motor, for a marine vessel, comprising: an engine or power plant (E), such as an internal combustion; a drive transmission for transmitting or transferring mechanical power generated by the engine or power plant (E) to a propeller shaft for generating propulsion for the vessel; a casing (3) that houses or at least partially encloses the engine (E) and/or the drive transmission; a mounting assembly (2) configured to mount the marine drive unit (1) to a hull, preferably to a transom, of the marine vessel; and a gyrostabiliser (4) arranged in or on the mounting assembly (2) or the casing (3). As an alternative to an outboard motor, the marine drive unit (1) may be provided as a stern drive unit or a pod drive unit. The invention also provides a marine vessel incorporating such a drive unit (1).