Chlamydia trachomatis ( Ct ) is the most common bacterium responsible for sexually transmitted infections. It constitutes a major public health burden, with the greatest clinical impact occurring in women of reproductive age. A vast proportion of Ct infections are underestimated because they are asymptomatic in nature. This leads to chronic infections with severe consequences, such as ectopic pregnancy, tubal obstruction, infertility, and blindness. Ct is an obligate intracellular pathogen that completes its entire developmental cycle in humans. Here, we demonstrate that galectin-1 (Gal1), an endogenous glycan-binding protein, promotes Ct –host adhesion and invasion. Through glycosylation-dependent mechanisms, Gal1 enhances chlamydial infection by favoring Ct –host cell interactions. Thus, novel therapeutic approaches aimed at disrupting Gal1– N -glycan interactions may reduce the severity of Ct infections.