Osteomalacia is a bone disease producing increasingly soft, brittle, flexible, and deformed bones because of a loss or shortage of calcium salts, or inadequate or delayed mineralization of osteoid in mature and spongy bone. Osteomalacia is often referred to as the adult form of rickets.

The incidence of osteomalacia is reported to be less than 0.1% in developed countries. In areas with high vegetarian populations, it has been reported to be as high as 15%.

Osteomalacia is produced by a metabolic disorder for which the underlying disease needs to be diagnosed.