In organic chemistry, an aminal or aminoacetal is a functional group or type of organic compound that has two amine groups attached to the same carbon atom: −C(NR₂)(NR₂)−. (As is customary in organic chemistry, R can represent hydrogen or an alkyl group).^[1] A common aminal is bis(dimethylamino)methane, a colorless liquid that is prepared by the reaction of dimethylamine and formaldehyde:^[2]

2 (CH₃)₂NH + CH₂O → [(CH₃)₂N]₂CH₂ + H₂O

Aminals are encountered in, for instance, the Fischer indole synthesis. Several examples exist in nature.^[3]

• Naturally occurring aminals
• 
  Physostigmine,a highly toxic cholinesterase inhibitor found in the Calabar bean.
• 
  Hodgkinsine, an alkaloid with antiviral, antibacterial and antifungal effects
• 
  5,10-Methylenetetrahydrofolate, an intermediate in one-carbon metabolism

Hexahydro-1,3,5-triazine ((CH₂NH)₃), an intermediate in the condensation of formaldehyde and ammonia, tends to degrade to hexamethylene tetraamine.

Cyclic aminals can be obtained by the condensation of a diamine and an aldehyde.^[4] Imidazolidines are one class of these cyclic aminals.