A homotetramer, a protein complex, which consists of four identical protein subunits which, although connected, but not covalently. A heterotetramer, however, is a protein complex of four subunits, wherein at least one of the other sub units differs. Both are among the tetramers.

Examples of homotetramers would be enzymes such as β -glucuronidase ( see picture); Export factors such as SecB in Escherichia coli and magnesium - ion transporter CorA like.