The φC31 attP (phage attachment) site is a non-coding DNA sequence naturally present in the genome of Lomovskayavirus C31 (previously known as Streptomyces bacteriophage φC31), where it serves as a recognition site for φC31 integrase. The integrase catalyses site-specific recombination between attP and the bacterial attachment site attB, resulting in integration of the phage genome and formation of the hybrid attachment sites attL and attR. The minimal functional attP site has been defined as approximately 39 bp. The φC31 attP/attB recombination system has subsequently been adapted for site-specific genome engineering, including the generation of transgenic insects, where a genomic attP site can serve as a predefined integration or “landing” site for attB-containing donor DNA.