Polymastia may refer to:
*
Accessory breast
Accessory breasts, also known as polymastia, supernumerary breasts, or ''mammae erraticae'', is the condition of having an additional breast. Extra breasts may appear with or without nipples or areolae. It is a condition and a form of atavism wh ...
s
*
Polymastia (sponge)
''Polymastia'' is a genus of sea sponges containing about 30 species. These are small to large encrusting or dome-shaped sponges with a smooth surface having many teat-shaped projections (papillae). In areas of strong wave action, this genus
...
, a genus of sponge
{{disambig