A breast implant (colloquially known as a boob job) is a prosthesis used to change the size, form, and texture of a woman’s breast; in plastic surgery, breast implants are applied for post–mastectomy breast reconstruction; for correcting congenital defects and deformities of the chest wall; and for aesthetic breast augmentation.

Breast augmentation surgery involves using breast implants or fat, to increase the size of breasts or restore breast volume that has been lost after weight reduction, pregnancy, congenital defects, or breast cancer excision.

There are three general types of breast implant devices, defined by their filler material: saline solution, silicone gel, and composite filler.

The saline implant has an elastomer silicone shell filled with sterile saline solution; the silicone implant has an elastomer silicone shell filled with viscous silicone gel; and the alternative composition implants featured miscellaneous fillers, such as soy oil, polypropylene string, etc. In surgical practice, for the reconstruction of a breast, the tissue expander device is a temporary breast prosthesis used to form and establish an implant pocket for emplacing the permanent breast implant.

For the correction of male breast defects and deformities, the pectoral implant is the breast prosthesis used for the reconstruction and the aesthetic repair of a man’s chest wall (see: gynecomastia and mastopexy).