Aldehyde dehydrogenases (ALDHs) are indispensable enzymes that play a pivotal role in mitigating aldehyde toxicity by converting them into less reactive compounds. Despite the availability of fully sequenced Azospirillum genomes in public databases, a comprehensive analysis of the ALDH superfamily within these genomes has yet to be undertaken. This study presents the identification and classification of 17 families and 31 subfamilies of ALDHs in fully assembled Azospirillum genomes. This classification system framework provides a more comprehensive understanding of the diversity and redundancy of ALDHs across bacterial genomes, which can aid in elucidating the distinct characteristics and functions of each family. The study also proposes the adoption of the ALDH19 family as a powerful phylogenetic marker due to its remarkable conservation and non-redundancy across various Azospirillum species. The diversity of ALDHs among different strains of Azospirillum can influence their adaptation and survival under various environmental conditions. The findings of this study could potentially be used to improve agricultural production by enhancing the growth and productivity of crops. Azospirillum bacteria establish a mutualistic relationship with plants and can promote plant growth by producing phytohormones such as indole-3-acetic acid (IAA). The diversity of ALDHs in Azospirillum can affect their ability to produce IAA and other beneficial compounds that promote plant growth and can be used as biofertilizers to enhance agricultural productivity.