A one-piece molded orthotic insert having a shape for controlling and directing the motions of the foot. The insert has a unitary body that is formed of a rigid, resiliently flexible, substantially noncompressible material, so that the insert will flex with the shoe but will not compress or deform, so that a correct shape is maintained through the gait cycle. The insert includes a raised arch portion that is supported by a plurality of underlying, vertical ribs. The ribs are spaced apart and free from connection with one another, so that the lower edges of the ribs are able to spread as the insert flexes along its lengthwise axis, so that the insert flexes generally uniformly when walking and without distortion of its shape. The layer of material overlying the ribs has a thickness generally similar to that in the reset of the body, and the ribs also have a generally similar thickness, facilitating manufacture by injection molding. A depending ridge extends around the lower surface of the insert for pressing into an insole so as to stabilize the insert against sliding or shifting in the shoe. The present invention provides many of the advantages of a custom orthotic using a more economical insert, and due to its thin vertical height it is especially suited for use with dress shoes.