Ethers ( /ˈiːθər/) are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether" (CH₃-CH₂-O-CH₂-CH₃). Ethers are common in organic chemistry and pervasive in biochemistry, as they are common linkages in carbohydrates and lignin.

Ethers feature C-O-C linkage defined by a bond angle of about 104.5° and C-O distances of about 140 pm. The barrier to rotation about the C-O bonds is low. The bonding of oxygen in ethers, alcohols, and water is similar. In the language of valence bond theory, the hybridization at oxygen is sp³.

Oxygen is more electronegative than carbon, thus the hydrogens alpha to ethers are more acidic than in simple hydrocarbons. They are far less acidic than hydrogens alpha to carbonyl groups (such as in ketones or aldehydes), however.

1) Simple ethers or symmetrical ethers 2) Mixed ethers or asymmetrical ethers