球菌（拉丁语：coccus，复数cocci）是一类外观呈球形或近似球形的细菌。

根据排列方式的不同，球菌可分为单球菌、双球菌、链球菌、四联球菌、八叠球菌以及葡萄球菌等。

• 葡萄球菌

A coccus (plural cocci) is any bacterium that has a spherical, ovoid, or generally round shape. It is one of the three distinct bacterial shapes, the other two being bacillus (rod-shaped) and spiral-shaped cells.

Coccus is an English loanword of a modern or neo-Latin noun, which in turn stems from the Greek masculine noun kokkos (κόκκος) meaning "berry".