Leptospira spp. are unique, long, thin, flexible rods with a helical shape and periplasmic flagella. They are highly motile, aerobic or microaerophilic bacteria that thrive in soils and aquatic environments but not marine environments. Leptospira spp. are divided into two main clades: "Saprophytes" and "Pathogens," with the latter causing leptospirosis, an emerging zoonotic disease. The genus Leptospira comprises 64 different species, with recent advancements in whole-genome sequencing expanding the number of identified species. Pathogenic Leptospira species, such as *L. interrogans*, have developed strategies to rapidly disseminate and evade the host immune system, including the presence of endoflagella and the production of adhesins. Genomic comparisons between pathogenic and non-pathogenic species have revealed significant differences in virulence factors, with more virulent species having a higher number of genes encoding these factors. Despite the high burden of leptospirosis, there is a significant gap in understanding its epidemiology and the basic biology of the bacterium.Leptospira spp. are unique, long, thin, flexible rods with a helical shape and periplasmic flagella. They are highly motile, aerobic or microaerophilic bacteria that thrive in soils and aquatic environments but not marine environments. Leptospira spp. are divided into two main clades: "Saprophytes" and "Pathogens," with the latter causing leptospirosis, an emerging zoonotic disease. The genus Leptospira comprises 64 different species, with recent advancements in whole-genome sequencing expanding the number of identified species. Pathogenic Leptospira species, such as *L. interrogans*, have developed strategies to rapidly disseminate and evade the host immune system, including the presence of endoflagella and the production of adhesins. Genomic comparisons between pathogenic and non-pathogenic species have revealed significant differences in virulence factors, with more virulent species having a higher number of genes encoding these factors. Despite the high burden of leptospirosis, there is a significant gap in understanding its epidemiology and the basic biology of the bacterium.