A self-lubricating swivelling coupling for interconnecting lines, includes a housing with internal surfaces defining a cavity. It also includes a male component, including a shank and a flange provided on the shank, insertable within the cavity to enable the flange to be abuttable on the internal surfaces. The coupling also includes a nut securable within the cavity, to abut axially via an internal axial projection on the flange, and to surround the shank, allowing the male component to rotate. The fluid leaks between the components to lubricate the coupling. Lines are connectable to ports to be swivellably interconnected without needle- or ball-bearings. There is high surface contact and support between the flange, shank and nut, to withstand and distribute forces. Hydraulic fluid is preferred. A seal-unit between the male component and the nut, and a slide-ring between the flange and the nut, are also preferred.