Ski braking devices are described for braking skis when they become accidentally detached from skiers' boots so as to bring the skis to rest in safe positions without hurting the skiers or other persons. Each described device has a frame with spaced parallel plates extending across the ski and a braking lever pivoted between them about an axis at one edge of the ski. A pivoted holding device snaps over the lever to hold it in an inoperative position in which it lies over the ski. When putting on the ski, the skier releases the holding device, for example with his boot, but the braking lever is retained in the inoperative position by the boot. On being released, the holding device is swung away from the braking lever by spring action. When the ski becomes detached, a spring swings the braking lever through about 270.degree. so that it projects downwards into the snow. On reaching this braking position, the spring shifts the braking lever along its axis to bring locking members into engagement and thereby fix the braking lever with respect to the frame. The braking lever is a flat plate and may be formed with a recess in which is pivoted a braking flap that lies in the plane of the braking lever when in the inoperative position but when the lever swings to its operative position, is caused by its inertia to swing out to a position perpendicular to the braking lever, in which the flap is automatically locked to the lever so that the flap presents its face to the direction of ski movement.