The Slingsby T.13 Petrel was a British single-seat competition glider built by Slingsby Sailplanes just before World War II.

The Slingsby Petrel was a development of the German DFS Rhonadler designed by Hans Jacobs. It was a single-seat high-performance sailplane with a span of a little under 18 metres, built of wood with a mixture of plywood and fabric covering. It had high cantilever gull wings, though the inner section dihedral was modest. They carried straight taper to fine and rounded tips and ailerons that extended over more than half the span. There were neither flaps nor airbrakes.

The fuselage had its maximum diameter near the nose, where the long, multipiece canopy blended in smoothly, ending at the wing leading edge. Behind the wings the fuselage tapered and became slender at the tail. The fin and the tailpane were both small in area; the rudder was large, aerodynamically balanced and extended down to the keel. The elevators were tapered, with a cut out for rudder movement. The undercarriage consisted of just a main skid from below the front of the cockpit glazing to mid chord plus a tail bumper.