An osteoblast (from the Greek words for "bone" and "to build") is a cell which produces osteoid.

Osteoblasts arise when osteoprogenitor cells (mesenchymal cells), which are located near all bony surfaces, differentiate under the influence of FGF, PDGF, TGF-beta and other bone morphogenetic proteins .

In addition to osteoid, osteoblasts also secrete enzymes which facilitate mineral deposition within osteoid matrices. They are also responsible for regulating the activity of osteoclasts via soluble mediators.

As osteoblasts age, they become osteocytes.