During sequencing of the genome of Clostridium perfringens strain 5147-97, a putative prophage was identified, located within a gene for a proposed flavodoxin oxidoreductase. Mitomycin C induction of this strain released a bacteriophage whose morphological features examined by electron microscopy indicated it belonged to the family Siphoviridae. This phage was hence designated as vB_CpeS-CP51. The 39,108-bp genome includes 50 predicted open reading frames (ORFs), including two that may affect sporulation, and two predicted tRNAs. To determine the ends of the prophage, PCR was performed using primers facing outwards from the proposed end genes. This confirmed the presence of a circularised genome in PEG-precipitated bacteriophage particles.