Production of carboxylic acids from alcohols is an important process for both industry and laboratory. Traditional methods usually require environmentally unfriendly oxidants and generate stoichiometric waste. Recently, methods using O
as oxidant, oxidation processes applying stoichiometric hydrogen acceptors and acceptorless dehydrogenative coupling reactions to generate carboxylic acids/carboxylic acid salts have been developed. This chapter reviews the reported results on the generation of carboxylic acids/carboxylates by acceptorless dehydrogenative coupling of alcohols and water. The chapter is according to the types of catalysts used; reaction conditions, product yields, and mechanisms are also discussed.