二元化合物指包含两种不同元素的化合物，如NaCl（氯化钠）和NaF（氟化钠）。

一般地讲，二元化合物的命名遵循两个形式：

A binary compound is a chemical compound that contains exactly two different type of elements. Examples of binary ionic compounds include calcium chloride (CaCl₂), sodium fluoride (NaF), and magnesium oxide (MgO), whilst examples of a binary covalent compounds include water (H₂O), and sulfur hexafluoride (SF₆).