The emergence and spread of multidrug-resistant and super-resistant bacterial strains have positioned phage therapy as a highly promising approach for future infection treatments. Klebsiella pneumoniae, a leading cause of clinical infections and hospital-acquired diseases, is responsible for over 95% of infections within the Klebsiella genus. Phages targeting K. pneumoniae exhibit remarkable diversity, with numerous isolates identified against various serotypes of this pathogen. In this study, we described the isolation and characterization of a novel bacteriophage from hospital sewage, Henu2_3, which targeted clinical isolates of K1-type K. pneumoniae. Transmission electron microscopy revealed that phage Henu2_3 possessed an icosahedral head and podovirus morphotype. The phage genome comprises 42,878 base pairs with a G + C content of 53.97%, encoding 54 putative open reading frames. One-step growth curve analysis demonstrated that phage Henu2_3 has a latency period of 10 min and an average burst size of 215 phage particles per infected cell. Additionally, Henu2_3 exhibited remarkable stability, tolerating temperatures up to 60℃ and maintaining maximum viability across a broad pH range of 4 to 12. In vivo infection models demonstrated that phage Henu2_3 markedly enhanced animal survival and decreased bacterial burden in target organs. These properties highlight its potential as a therapeutic agent against K. pneumoniae infections.