Abstract: A marine riser system for a petroleum production platform or other structure includes a central support column extending from a subsea manifold vertically upward to a connection with a riser tensioner assembly mounted on a floating platform. The central support column includes one or more vertically spaced levels of radially extending arms which are pivotally connected to the central support column and are held in generally horizontally projecting positions by individual hydraulic cylinder actuators. Each of the support arms is adapted to be connected to a riser conduit and to apply a predetermined upward tension to the conduit whereby the entire riser system is maintained under a predetermined tension with respect to the support column and to permit motion of the platform structure under varying sea conditions. The riser system includes a plurality of vertically spaced apart guide funnels supported on sets of foldable arms.