Geminal halide hydrolysis is an organic reaction. The reactants are a geminal dihalide and water or a hydroxide. The reaction product is a ketone or an aldehyde. The first part of the reaction mechanism consists of an ordinary nucleophilic aliphatic substitution to produce a gem-halohydrin. The remaining halide is a good leaving group and this enables the newly created hydroxy group to revert to a carbonyl group expelling the halide. Similar reactions involving any strong electronegative functional group, such as a nitrile, in place of the halide also occur.
In a similar fashion 1,1,1-trihalides are hydrolyzed to carboxylic acids in the haloform reaction.